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December 23

fiberglass rot

When fiberglass rots I assume the resin is what rots and not the silicon dioxide fiber. By what organism does this rot occur? 71.100.6.206 (talk) 00:10, 23 December 2009 (UTC)

It could just be some chemical degradation. Light, oxidation, there are a host of ways that something can "break down" that don't involve organisms. --Jayron32 00:13, 23 December 2009 (UTC)

Fiberglass is just glass, there is no resin. Do you mean Fiber reinforced plastic? Ariel. (talk) 02:38, 23 December 2009 (UTC)

Ariel, Did you even read the article you linked? Here is the second sentence "It is used as a reinforcing agent for many polymer products; the resulting composite material, properly known as fiber-reinforced polymer (FRP) or glass-reinforced plastic (GRP), is called "fiberglass" in popular usage." APL (talk)

And the pink stuff that they sell as insulation is called what? It's called fiberglass, and it actually is just glass, with no resin or anything else. At least call the other stuff fiberglass panels/boards, etc. Ariel. (talk) 05:25, 23 December 2009 (UTC)

You are both right - according to Wiktionary the word has two distinct meanings:

1. silica based glass extruded into fibers that possess a length at least 1000 times greater than their width.
2. a composite material made from fine fibres of spun glass held together with resin. (Also called Glass-Reinforced Plastic.)

In (1) there is nothing but glass - and that's what you find in roof insulation and optical fibre. In (2) there is resin holding the fibreglass filaments together - but the resulting material is still called fibreglass...it's the stuff they make boat hulls from, for example. When type (2) fibreglass degrades it's generally because UV light has degraded the epoxy. The glass fibres are not degraded - so type (1) lasts pretty much forever (at least on "human timescales"). There are various coatings they can put on the material to reduce the UV breakdown - but it seems that none of them are perfect. SteveBaker (talk) 12:53, 23 December 2009 (UTC)

IMHO I agree with APL here. Ariel is right that fiber-reinforced polymer is a better name but our article itself makes clear early on it's commonly called fibreglass. If Ariel read the fibreglass article and/or understood this already then I would suggest a better answer would have been "fibreglass properly only refers to stuff that is just glass, you're probably thinking of fibre reinforced polymer which is common called fibreglass but which has resin in between the fibres and comes in boards and panels" or something of that sort since that's far more helpful to the OP and question answerers Nil Einne (talk) 14:10, 23 December 2009 (UTC)

But why correct the person at all when they are communicating effectively and properly using the common name of a substance? With the mention of "Resin" it was 100% clear to everyone what was meant. It's not as if the linked articles answered the question. APL (talk) 01:06, 24 December 2009 (UTC)

In my experience the fluffy insulation is called 'glass fibre', while 'fibreglass' means the bonded stuff. --ColinFine (talk) 17:38, 24 December 2009 (UTC)

Getting a bit too OT so taking to talk page Nil Einne (talk) 12:10, 25 December 2009 (UTC)

UV degradation of the resin is a big part. Store in shade. Polypipe Wrangler (talk) 12:23, 26 December 2009 (UTC)

Per-unit-cost energy content of different battery sizes

Of the several common battery sizes (AA, AAA, C, & D), which of them tends to give you the most energy on a per unit cost basis? --173.49.11.197 (talk) 00:19, 23 December 2009 (UTC)

Usually larger sizes are more cost effective, but D size is rare(ish), so may be more expensive. Battery (electricity)#Life of primary batteries and List of battery sizes has a chart with capacities, so you can do your own math. Be aware that rechargeables are different (but should have the capacity listed on the package), and that some battery manufacturers cheat, and put a rechargeable AA inside a C and D shell. Ariel. (talk) 02:43, 23 December 2009 (UTC)

Icosahedrons or Dodecahedrons?

If perfect (or nearly perfect) spheres are crushed together with equal pressure from all directions (similar to what one might expect when lowering a weighted bag of ping-pong balls or balloons into the depths of the ocean) will their interfacing surfaces form Icosahedrons or Dodecahedrons? 71.100.6.206 (talk) 00:32, 23 December 2009 (UTC)

How many spheres? How are they situated in the bag? What's the motivation and context for this question? ~~ Dr Dec (Talk) ~~ 00:34, 23 December 2009 (UTC)

See Sphere packing. You won't get either as they can't be arranged in a packing. People have actually tried the experiment with balls randomly thrown into a box. Dmcq (talk) 00:41, 23 December 2009 (UTC)

I was under the impression that the spheres got squashed by the pressure and lost their shape. This isn't the same as sphere packing where the spheres remain rigid. ~~ Dr Dec (Talk) ~~ 00:44, 23 December 2009 (UTC)

No, but it sounds like a related problem. You need to start with a sphere packing and then crush the spheres together. What you end up with will depend on what sphere packing you started with. --Tango (talk) 01:12, 23 December 2009 (UTC)

You can get most any shape you want. You can get cubes, if the spheres start out in that pattern. Perhaps you are asking what is the tessellation with the greatest ratio of volume to surface area. Which is another way of saying you want the best sphere packing. Ariel. (talk) 01:11, 23 December 2009 (UTC)

If you drop spheres into a container randomly you will most likely get sphere close packing. The polyhedron packing that most closely corresponds to this is a truncated octahedron honeycomb, so I am guessing that is what crushing under pressure will get you. To get a cube honeycomb you would have to carefully pack the spheres in a cubic honeycomb before crushing - which is quite difficult as the spheres will not naturally stay lying in that configuration. SpinningSpark 01:36, 23 December 2009 (UTC)

Truncated octahedrons are a space-filling geometry, but I don't know if you could get them by squishing spheres together. Nimur (talk) 01:53, 23 December 2009 (UTC)

The results of circles so treated in 2 dimensions is a honeycomb as stated. I'm merely looking for the same results in 3 dimensions using spheres starting with a regular lattice. 71.100.6.206 (talk) 02:06, 23 December 2009 (UTC)

No, it's not. If you start with your circles in a square grid, and squish evenly on the sides, you will get squares, not honeycombs. And you got an answer: truncated octahedron. BTW circle packing is not 100% definitively proven, so there is no definitive answer to your question. (Assuming that your real question is "what space-filling shape maximizes volume to surface area". Since your actual question has no answer.) Ariel. (talk) 02:30, 23 December 2009 (UTC)

Oooh, this paper is interesting. The guy has actually done the experiment with soap bubbles and gets the conclusion that the resulting honecomb is irrational. SpinningSpark 03:06, 23 December 2009 (UTC)

That paper is about randomly placed spheres. I think the OP wants a regular close packing. Dauto (talk) 03:53, 23 December 2009 (UTC)

The shape the OP is looking for is the Rhombic dodecahedral honeycomb. Dauto (talk) 03:47, 23 December 2009 (UTC)

Correct on both counts... Thanks Dauto! 71.100.6.206 (talk) 04:37, 23 December 2009 (UTC)

Sorry I thought the sphere packing article would mention that or link to it, I'll go and put in a link. Dmcq (talk) 11:10, 23 December 2009 (UTC)

I like rhombic dodecahedra, particularly because of the disconcerting way they look like cubes from most angles. [1]

[2] [3] Felis cheshiri (talk) 15:51, 23 December 2009 (UTC)

The comparative values of specific health behaviours

I'm aware of the standard advice regarding healthy behaviour (for example, don't smoke, stay slim, take exercise, avoid saturated fats, eat plenty of fruit and vegetables). But I'm wondering if the comparative worth of these different behaviours has been published anywhere? Knowing that, for example, that staying slim was worth 100 times more than eating X amount of fruit&veg every day would motivate weight-loss, and increase dedication to the most valuable behaviour. 92.29.68.169 (talk) 13:39, 23 December 2009 (UTC)

I don't think you'll find definite numbers like that, partly because there is some disagreement and partly because all of these behaviours exist on a continuum and interact with each other, your genes, and other aspects of your environment. For example, cutting down on salt would have a minimal impact on most people's health, but for a few people it would drastically increase their lifespan because they are sensitive to salt. And there is no procedure to identify these people before they are talking to a doctor about their serious health problems. 86.176.191.243 (talk) 14:26, 23 December 2009 (UTC)

Official government advice (5 A Day) seems to disagree with this notion that we are all different. Felis cheshiri (talk) 16:11, 23 December 2009 (UTC)

Of course, the article that you linked notes that these nominally-similar programs offer different advice in different countries. Do Americans actually need eight times more fruit than Britons? It seems unlikely. 'Official government advice' is going to be based on some combination of best guesses, old data, received wisdom, studies in other countries, expert consultion, powerful lobby groups, typographical errors, and political biases. The advice that makes it into the final pamphlet is going to be based largely on the practices which, in the aggregate, tend to produce an overall improvement without doing significant harm to any individuals.

For example, recommending a moderate intake of sodium (salt) isn't goign to be harmful for anyone, and it can significantly reduce hypertension (and associated morbidity) in individuals who are particularly sensitive to sodium. The net result is a (small) overall increase in average health, though most of that improvement is going to be due to major gains in a smaller fraction people. Similarly, an individual who has a family history of type 2 diabetes is likely to derive a greater potential benefit (delay or evasion of disease progression) than the average person from exercise and a healthy diet — but exercise and diet improvements will probably offer at least some benefit to nearly everyone. TenOfAllTrades(talk) 16:39, 23 December 2009 (UTC)

The Wikipedia article about the difference in UK and US portion sizes is misleading: if you read the source site, the UK "one tablespoon" portion size only refers to dried fruit, for other types of fruit and vegetables the portion sizes are similar to those in the US. I have now edited the article to remove the misleading information. 92.29.51.193 (talk) 20:22, 23 December 2009 (UTC)

I have added the curious fact about dried fruit after your edit, in a non-misleading way. Felis cheshiri (talk) 20:53, 23 December 2009 (UTC)

I have now looked at the souces given in the article: I quote from what I wrote on the discussion page - "The article says the US and UK portion sizes are eight times different. Not true if you look at the souces given: the US sources do not mention dried fruit except for "1 small box (1/4 cup) of raisins", and the UK source mentions "1 tablespoon" of dried fruit. Tablespoons, different from dessert spoons, are big things so the portion size is about the same. Also, it unimportant and insignificant if the portion sizes (for dried fruit) are different.". Please remove the misleading information. Update: the confusion may be do to differences in US-english and UK-english: in the UK a tablespoon is a very large spoon. The Wikipedia tablespoon article appears to be about what we in the UK would call a dessert spoon. See the discussion page to that article. A heaped tablespoon (in UK-english) would probably be much more than the two fluid ounces referred to as the US dried-fruit portion size. 78.149.147.198 (talk) 23:13, 23 December 2009 (UTC)

Alright, I bow to your accuracy. :) Felis cheshiri (talk) 01:04, 24 December 2009 (UTC)

I respectfully disagree, and have said so on the tablespoon talk page. I have supported my assertion with a reference from Delia Smith and some OR based on a 30 year old UK tablespoon. Felis was right. 86.176.191.243 (talk) 01:18, 24 December 2009 (UTC)

From my personal experience of UK tablespoons and UK dessert spoons, I have to disagree with you. A tablespoon was much larger than a dessert spoon. The size was not standardised, so you must have come across a smaller one. Tablespoons are now rare in the UK due to changes in cooking and eating styles. 78.146.200.137 (talk) 11:04, 24 December 2009 (UTC)

Turns out the UK's 5 A Day recommendations are based on (among other sources) "the Leatherhead report", summary available here: [4] which states that (in this context, at least) a tablespoon = 15ml. If that's comparable to a quarter of a US cup, that gives us a 60ml cup rather than (minimum) 240ml, yielding a nice factor of 4 disparity. Felis cheshiri (talk) 13:47, 24 December 2009 (UTC)

You have made the same mistake again. The "tablespoon" (UK-english) only refers to dried fruit, not fruit and veg in general. As described in tedious detail on the discussion page to the five-a-day article, the US portion size for dried fruit is very similar. Note that raisins are a type of dried fruit. 92.24.73.139 (talk) 15:01, 27 December 2009 (UTC)

As the previous response notes, there are significant and not-fully-understood genetic factors which can make some individuals more susceptible than others to particular habits. It's important to remember that any particular numbers related to loss of life expectancy are aggregate statistics, and that any individual's response to a given lifestyle choice will ultimately depend on their own genetics, the interplay of assorted environmental and lifestyle factors, and sheer dumb luck.

That said, there's a brief summary of a couple of large studies which mostly focused on obesity here. Most studies find an 'optimum' body mass index somewhere between 22 and 25. Being mildly overweight (BMI up to about 30) doesn't tend to have huge penalties, particularly as one grows older. (I have seen speculation that a modest amount of excess fat provides a 'cushioning' effect during periods of illness when one might not tend to consume enough calories, particularly among the elderly.) Being significantly overweight when you're a young adult hurts you more than growing overweight as you age. BMI between 30 and 35 costs you (statistically speaking) 2 to 4 years. BMI of 40 to 45 knocks down median survival by 8 to 10 years; smoking carries roughly the same 8- to 10-year penalty. Being underweight (BMI less than about 20) also is linked to excess mortality.

That said, the apparent power of BMI as a predictor should not be taken to mean that merely being somewhat overweight is a cause of excess mortality. Factors such as poor diet or a lack of exercise can cause both disease and obesity. A 2007 study of seniors (discussed here) found that obese individuals (BMI from 30 to 35) who were 'fit' (based on a treadmill test) had a significantly reduced mortality compared to 'unfit' people of normal weight.

I don't have comparable numbers for nutrition. The challenge there is that while weight is easy to quantify and track (and often recorded regularly and consistently by physicians and patients) it is much more difficult to get accurate data on everything that a large cohort of individuals eats. TenOfAllTrades(talk) 15:22, 23 December 2009 (UTC)

Density of heavy water

I was wondering why the density of pure heavy water is not 2g per cc as it contains one proton and one neutron per atom and as the neutron is about the same mass as a proton and I assume the atomic radius of water and heavy water molecule the same. —Preceding unsigned comment added by 41.212.208.234 (talk) 14:35, 23 December 2009 (UTC)

Heavy water contains one proton and one neutron per atom of hydrogen. However, water is not pure hydrogen. The mass of the oxygen does not change, and so the mass of the molecule does not double. — Lomn 14:46, 23 December 2009 (UTC)

(After edit conflict) You have forgotten the 16 protons and neutrons in the oxygen atom. A molecule of D₂O contains 20 nucleons whereas H₂O contains 18, so you would expect density of D₂O to be about 20/18 = 1.11 g/ml, which is approximately correct. Gandalf61 (talk) 14:48, 23 December 2009 (UTC)

It's also possible to get water with a heavy isotope of oxygen (up to 2 extra neutrons) to make even heavier water. I believe it's used in some medical tests. Ariel. (talk) 18:34, 23 December 2009 (UTC)

(ec) Normal water has two hydrogen atoms (one proton each) and an oxygen atom (8 protons and 8 neutrons). Heavy water has one normal hydrogen atom, one deuterium atom (one proton and one neutron) and one oxygen atom. That means you have a total of 19 nucleons compared to 18. So the density ought to be about $1{\frac {1}{18}}$ grams per cc. Of course, actual heavy water is a mixture of H₂O, HDO and D₂O. --Tango (talk) 14:51, 23 December 2009 (UTC)

A minor quibble about terminology. 'Heavy water' should not be assumed to mean a 1:1 ratio of protium (regular 'light' hydrogen) and deuterium. In my experience, heavy water almost always means pure deuterium oxide (that's all you get if you look for 'heavy water' in the Sigma catalog), although IUPAC seems to be more flexible, accepting any "Water containing a significant fraction (up to 100 per cent) of deuterium in the form of D₂O or HDO"[5]. TenOfAllTrades(talk) 15:34, 23 December 2009 (UTC)

Indeed, the terminology is not consistently used. It depends on context. Some uses of heavy water need almost pure D2O, others just need a higher than usual ratio of D to H. What people call "heavy water" will depend on what use they are putting it to. If the OP meant pure D2O then the density should be changed to $1{\frac {1}{9}}$g/cc. --Tango (talk) 15:38, 23 December 2009 (UTC)

Totally interjecting here, but I never expected an extra two neutrons per molecule would make such a difference as .11 g/ml. Does this mean that heavy water would sink to the bottom of a tank of regular H₂O? Ks0stm ^(T•C•G) 15:23, 23 December 2009 (UTC)

No, because the two liquids are not immiscible - the heavy water molecules will dynamically combine with the ordinary water molecules to create a homogenous mixture of H₂O, HDO and D₂O. But our heavy water article does say that heavy water ice will sink when placed in ordinary water. Gandalf61 (talk) 15:31, 23 December 2009 (UTC)

There will be some separation with a concentration of heavy water at the botton slightly higher than at the top. But the difference will be small at 1 g gravity. Higher concentrations can be achieved with centrifuges. Dauto (talk) 17:07, 23 December 2009 (UTC)

Average time of sunlight worldwide

If we ignore issues such as topography, is there anywhere in the world in which the sun is not above the horizon for about 2,190 of the 4,380 hours in a non-leap year? I'm pretty sure that the answer would be no, since places on the Equator have equal amounts of sunlight every day, and anywhere else in the world, it seems that the amount of daylight in any given day and the amount of night exactly six months away would be equal, but I could be forgetting to account for something. Nyttend (talk) 22:21, 23 December 2009 (UTC)

If we ignore topography then I think that is right. It should all average out. If we do count topography then it can be very different (eg. see Viganella). --Tango (talk) 22:53, 23 December 2009 (UTC)

You are asking if there is anyplace where there is an imbalance in day vs night, as measured over a year? I would have to say yes for two reasons.

1: Because the sun is a point source, but darkness covers everything else - they two are not symmetrical (it's not half light, half dark). Let's assume the earth was not tilted - the poles would never get any light. The poles are tilted of course, but the intensity of their light (add up all the light energy they receive in a year) is less than the total intensity of light in the equator - but the "intensity" of darkness is the same for both. This is not what you are asking though. You are asking if you can simply see the sun or not.

2: Let's assume the earth rotates on it's axis once per year. There would of course be places that get no light. Now lets assume twice per year, then simply because of the tilt of the earth, some places would get more than others because they happened to be tilted away from the sun during their moment in the light. Obviously the earth rotates faster than that - but it's not an integer number of rotations per year. So there are parts of the earth that get just a bit less sun than others because they happened be tiled away from the sun during their moment. The difference is probably small, but you seem to be looking for an exact answer. If you average over eons, it probably works out, but not averaged over a year. Ariel. (talk) 23:08, 23 December 2009 (UTC)

1:The sun is not a point source. It is infact larger than the earth.

2:True but completely negligible and probabily not the kind of precision the OP is looking for. His arbitrary exclusion of leap years shows he is not interested in those minor details. Other effects are more important such as refraction in the atmosphere. Dauto (talk) 23:42, 23 December 2009 (UTC)

The simple answer is yes, and this can be seen without considering atmospheric effects or the fact that the Sun is not a point source. Just remember that from the equinox in March until the one in September the Sun is continuously above the horizon as seen from the North Pole, and for the rest of the year it is continuously above the horizon as soon from the South Pole. But because the Earth moves faster in its orbit when closer to the Sun, and it's closest in January and farthest in July, the two equinoxes are not equally spaced -- the North Pole always gets more time in sunlight. Here's are the equinox dates for the years 2000-2020 from the United States Naval Observatory web site (all times are UTC), and I've added a column showing the elapsed time between them in days. Note that it is always longer than half a year (which is about 182.62 days).

 2000  Mar 20 07:35  Sept 22 17:28  186.41
 2001  Mar 20 13:31  Sept 22 23:04  186.40
 2002  Mar 20 19:16  Sept 23 04:55  186.40
 2003  Mar 21 01:00  Sept 23 10:47  186.41
 2004  Mar 20 06:49  Sept 22 16:30  186.40
 2005  Mar 20 12:33  Sept 22 22:23  186.41
 2006  Mar 20 18:26  Sept 23 04:03  186.40
 2007  Mar 21 00:07  Sept 23 09:51  186.41
 2008  Mar 20 05:48  Sept 22 15:44  186.41
 2009  Mar 20 11:44  Sept 22 21:19  186.40
 2010  Mar 20 17:32  Sept 23 03:09  186.40
 2011  Mar 20 23:21  Sept 23 09:05  186.41
 2012  Mar 20 05:14  Sept 22 14:49  186.40
 2013  Mar 20 11:02  Sept 22 20:44  186.40
 2014  Mar 20 16:57  Sept 23 02:29  186.40
 2015  Mar 20 22:45  Sept 23 08:21  186.40
 2016  Mar 20 04:30  Sept 22 14:21  186.41
 2017  Mar 20 10:29  Sept 22 20:02  186.40
 2018  Mar 20 16:15  Sept 23 01:54  186.40
 2019  Mar 20 21:58  Sept 23 07:50  186.41
 2020  Mar 20 03:50  Sept 22 13:31  186.40

In general, this reason means that places in the Northern Hemisphere will get more time of daylight than in the Southern Hemisphere. However, the effect is offset, and I believe more than offset, by the variation in distance of the Sun. --Anonymous, 23:51 UTC, December 23, 2009.

(ec) Well, we can also consider whether the sun is up for 2,202 of the 4,404 hours in a leap year; my point was simply exactly half a year. I was wondering if perhaps refraction would contribute, but I've never quite understood — how could this make the day seem longer or shorter? If it makes sunset seem to be later than it would if we had no atmosphere, how is it that sunrise doesn't appear to be several minutes later as well? Refraction doesn't cover the subject; I'll welcome a link to an article that does. Nyttend (talk) 23:55, 23 December 2009 (UTC)

The difraction makes the sun's light curve a little bit around the earth making the sun rise earlier and set later. Dauto (talk) 00:38, 24 December 2009 (UTC)

Since the sun is much bigger than the earth, can we not also say that more than half a sphere will be illuminated - so something like 181° rather than 180° - therefore the sun will always be showing above 2,190 hours  Ronhjones  ^(Talk) 00:11, 24 December 2009 (UTC)

I should think that the finite angular size of the sun as seen from earth should be the more important contributor. Sun has an angular diameter of about half a degree. So, even though the time for which one could see the sun at the equator if it were a point source is about 12 hours per day, this finite size increases the time by 2 minutes on the equinox day and even more on the other days. This effect becomes even more important closer to the poles (If the earth's rotation axis were perpendicular to the ecliptic, people at the poles could have seen the sun throughout the year). So what I believe is that the total time for which one can see the sun at any point on the earth is more than 50% when a year is considered -- Raziman T V (talk) 05:29, 24 December 2009 (UTC)

December 24

Earliest sunset

is there anywhere in the world where the sun can set before local noon? —Preceding unsigned comment added by 97.118.58.208 (talk) 00:08, 24 December 2009 (UTC)

Going back to the previous section, perhaps Viganella? Nyttend (talk) 00:13, 24 December 2009 (UTC)

Since noon is defined as halfway between sunrise and sunset, you can't have noon be after sunset. Unless you consider the sun being behind a mountain as sunset. Ariel. (talk) 02:20, 24 December 2009 (UTC)

That depends on your definition of 'noon'. In my experience, 'noon' is usually held to be synonymous with the midday 12 o'clock in whatever time zone I happen to be in. In principle, one could have a very short day (near the Arctic circle in midwinter, for instance) and be standing near the eastern edge of the time zone. Sunrise and sunset could follow in quick succession, and you could be back in the long night before the clock rolls over to twelve. Using this handy calculator, one can easily confirm this. Poking around a bit with Google Maps, the village of Pajala in northern Sweden meets the necessary criteria. On four days this year (19 December through 22 December) the time between sunrise and sunset is only about an hour, and the sunset falls before local 1200. TenOfAllTrades(talk) 03:03, 24 December 2009 (UTC)

If you define "local noon" as "the time halfway between sunrise and sunset", then by definition the answer is "no". If you define "local noon" as "12:00 according to the local time zone", then any place close to the arctic circle and offset far enough from the time zone's meridian can have sunset before noon. --Carnildo (talk) 02:44, 24 December 2009 (UTC)

The latter is also true if you define "local noon" as "noon according to local mean solar time" without reference to time zones, due to the equation of time. At the day of maximal equation of time (some 16 minutes), stand sufficiently far north of the arctic circle that the length of the day is less than half an hour. Then the sun will set before noon MST. –Henning Makholm (talk) 06:57, 24 December 2009 (UTC)

On the road between Todmorden and Bacup, Lancashire, England, there is a place which is in the shadow of a hill for about 3 months of the year. There is a small hamlet at the foot of the hill which casts this shadow, so this may well qualify as the answer to the question. --TammyMoet (talk) 16:00, 24 December 2009 (UTC)

Returning isolated human and immunity

Suppose we have an ordinary healthy human in his or her twenties who has lived his or her entire life in urban areas. Then, he or she spends three or four years in some kind of complete isolation from physical human contact (for example, an Antarctic research station or a solitary prison of some kind). During that time, he or she has plentiful access to food, water, living space, telecommunications, etc., everything necessary to stay in good physical and mental health. When he or she returns to the city, will he or she be more likely than the average person to catch the common cold or a seasonal flu, or is three or four years not long enough a period of isolation for it to matter with respect to medical immunity?

—Lowellian (reply) 01:46, 24 December 2009 (UTC)

No, however they may get a bunch of colds at once (which is probably indistinguishable from having just one), since they didn't get a chance to get them one at a time each year. Immunity in general lasts a lifetime. A person is also never sterile, even if you are not infected with visible illness your environment is full of bacteria, so the immune system never stops working. I think some lab animals are grown completely sterile, but it's quite hard to do. The bio-filter on the Star Trek Transporter would in actually be really bad, if it removed all bacteria from a person. Doing that would cause the immune system to go haywire, and would also cause all sorts of digestive and skin problems. Ariel. (talk) 08:27, 24 December 2009 (UTC)

I already know immunity lasts a lifetime and that even isolated environments are not sterile, but that's not the point. It's not what I'm asking, so let me try to clarify. Viruses and bacteria constantly mutate. That person who has been in isolation won't have immunity to any new strains that developed and spread among the human population during those three years. So, another way of looking at the question is, is the rate of new strain development fast enough that the person would be at significantly higher risk of getting sick than people who haven't been in isolation, or is the rate of new strain development slow enough that there would be no appreciable difference given a timespan of only three to four years? —Lowellian (reply) 09:10, 24 December 2009 (UTC)

The only way to get immunity to a cold is to get sick. People outside will get sick X number of times. The isolated person will also get sick when he emerges. Basically he's putting off getting sick for a while, but in net will get sick at the same rate as people outside. He's not reducing or increasing his risk, he is postponing it. And actually he might feel sick just once, and handle all the new stuff all at once, while the people outside had to do it one at a time. (Actually, the previous strains may no longer exist much in the wild, and he won't have to deal with them. People in general do not constantly shed viruses. There are only a limited number of diseases where you have chronic carriers.)

The rate of mutation of a cold is such that after 3 years there will probably be a new strain - I think it's fast enough that you have a new strain every year, but I could not find hard numbers. Is that your main question? How often does the cold/flu virus mutate to the point that people will get sick again? Ariel. (talk) 09:40, 24 December 2009 (UTC)

This year's flu is around for everyone to catch. Last year's mutation of the flu is not necessarily still around in enough numbers for the "returnee" to ever be exposed to it. (Especially true of this year's swine flu) 75.41.110.200 (talk) 14:55, 24 December 2009 (UTC)

Indeed. Ariel, your first paragraph above makes no sense. How many times have you caught black death? You weren't around for the first one, so presumably you're due to get in at any time, right? And if you don't have sex until you're sixty you'll catch herpes, the clap and crabs all at once to make up for all the STDs you should have gotten if you'd been having regular intercourse? Nature doesn't just force you to "catch up" somehow to make it all fair and even. What possible mechanism would be involved? Matt Deres (talk) 17:24, 24 December 2009 (UTC)

What paragraph are you talking about? Because I was the one who said that: "Actually, the previous strains may no longer exist much in the wild, and he won't have to deal with them. People in general do not constantly shed viruses. There are only a limited number of diseases where you have chronic carriers." Ariel. (talk) 18:11, 24 December 2009 (UTC)

My apologies. Your comment that "He's not reducing or increasing his risk, he is postponing it. And actually he might feel sick just once, and handle all the new stuff all at once, while the people outside had to do it one at a time" is what I was referring to, though you did obviously correct yourself in the bracketed comment. My bad. I would normally put the most correct answer in the regular part and perhaps add a parenthetical remark to acknowledge something that was conjecture rather than the opposite setup, but I still should have read your post more thoroughly. Matt Deres (talk) 18:23, 24 December 2009 (UTC)

Still same situation as posed above, but let me try asking this question another way. In a given month, there exists some probability p that an average non-isolated healthy person will get sick with the cold or flu at least once. Suppose the returnee comes back to the city that same month after three or four years in isolation. There also exists some probability q that the returnee will get sick with the cold or flu at least once that month. Is q going to be significantly higher than p? —Lowellian (reply) 00:42, 25 December 2009 (UTC)

Imperceptible. There should be a slightly increased probability if you investigated closely enough, but I reckon a sample size of many thousands of subjects would be necessary to show a statistically significant difference in a randomized controlled trial (the best answer medical science can give you). I know of no such study, and anecdotally I've never heard of terrible health problems in returning Arctic researchers, astronauts, Biosphere 2 workers, etc.

Crowded humans encounter numerous types of cold and flu virii; infection stimulates the formation of memory B cells against that specific virus. The crowded man simply gets more exposure during those 3 years, so he has more opportunity to develop immunity to the relevant pathogens. However, the number of different cold and flu strains is vast, and I think most of them won't have touched the crowded man significantly enough to give an advantage. Plus, the isolated man still has functional innate immunity (which deals with the majority of infections), and his adaptive immunity from before the isolation is still formidable.

For the seasonal flu specifically, it's often a relatively novel strain. In this case, it's even less likely that the crowded man would have had an exclusive opportunity to encounter it in the three year window. - Draeco (talk) 21:30, 25 December 2009 (UTC)

The answer is no, you will not be any more likely to catch a cold. There are too many diferent viruses floating around and they mutate too rapidly to make any difference. Gandydancer (talk) 03:38, 26 December 2009 (UTC)

Mass and Weight Physics

Can someone describe the difference between mass and weight?

When you stand on a weighing scale, is that weight or mass?

I'm just getting confused b/c like for a chemical reaction, a problem can say you have oxygen with a mass of 100g, but is that specific to that much oxygen on earth, or any other planet / in outer space?

thanks. —Preceding unsigned comment added by Legolas52 (talk • contribs) 07:30, 24 December 2009 (UTC)

Mass: the amount of matter. Weight: how strongly that matter is pulled by gravity. You are confused because since the easiest way measure how much matter there is, is by seeing how strongly it is pulled toward the earth, this strength of attraction is (was) used to also indicate how much matter there is.

When you stand on a weighing scale, the number shown is weight. But, knowing the weight, and the strength of the earth's gravity, it is possible to then calculate the mass. Ariel. (talk) 07:44, 24 December 2009 (UTC)

Thanks for your reply! But still, this is what I'm confused by - if in a chemistry problem, you are given a "mass" does it refer to its mass or is it weight labeled incorrectly. Or, moreover, does the scale correct for earth's gravity by dividing by 9.8 m/s^2? —Preceding unsigned comment added by Legolas52 (talk • contribs) 07:59, 24 December 2009 (UTC)

Chemistry is almost always concerned with amount of matter, that is, mass. Gravity is not involved at all, except indirectly as a cause of pressure, which does matter chemically. Conversely, if the chemistry problem talks about "weight", it is almost certainly using that word in its everyday usage where it is synonymous with mass. Only if the problem quotes the "weight" in newtons is there reason to even suspect that it means gravitational pull.

Practical scales do not explicitly "divide by 9.8". Even scales that work by measuring force (using springs or strain gauges) are simply calibrated in mass units from the beginning, tacitly assuming the local acceleration of gravity wherever the calibration took place. –Henning Makholm (talk) 08:15, 24 December 2009 (UTC)

Scales are a common source of confusion here. Although they measure weight, they are labelled in units of mass (kilograms). Strictly speaking, the scale should be labelled with the (non-SI) unit of force called the kilogram-force or kilopond. Your weight is not 100 kilograms, it is 100 kiloponds. Gandalf61 (talk) 09:36, 24 December 2009 (UTC)

Whether a weighing scale actually measures mass or weight depends on its construction. Your typical bathroom scale, which measures the amount of force your body exerts on it, actually measures weight. The kind of weighing scale used in a doctor's office actually measures mass. --173.49.78.112 (talk) 18:25, 24 December 2009 (UTC)

g and kg are units of mass, and so it is not really incorrectly labelled. Scales measure your mass by directly claculating your weight and assuming a force field of g perpendicular to the plate of the scales. —Preceding unsigned comment added by 92.17.229.48 (talk) 12:23, 24 December 2009 (UTC)

Try this explanation out. You have a block of wood. That block of wood has a specific mass. If you put it on a scale here on Earth, it will have a certain weight. That's because the Earth is pulling it down. Now you take that wood block to the Moon. It still has the same mass, since you haven't changed how much wood you have, but it's weight is smaller because the Moon is not as big as the Earth and doesn't have as much gravity. So, the mass is the same, the weight is different.

Now, as for chemistry. What is important is the mass and not the weight. Since mass is always the same wherever you are, that's the important part for chemistry. The amount of stuff that you have, the mass, is everything. What it weighs is not because if you have the same mass of stuff, the reaction should be the same on the Earth as it is on the Moon. Dismas|^(talk) 12:36, 24 December 2009 (UTC)

Lab balances I have seen, even in high school, measured mass, by having a standard mass on a slider and the to-be-measured chemical in the pan, perhaps with a standard mass in the other pan. Measured masses would be the same on the Earth or the Moon, where the gravity is about 1/5 as much. The digital gram scale I have in the kitchen, on the other hand, measures weight, by noting the depression of a spring or strain gauge via an electronic circuit. Things would weigh less on the Moon with it. Some analog kitchen gram scales are actually balances, using an eccentric counterweight which rotates under load. Edison (talk) 00:30, 25 December 2009 (UTC)

I believe weight is a relative measurement of mass, so while something's mass remains the same, the measurement of its weight can be different depending on the level of gravitational force in the location of measurement. --Neptunerover (talk) 07:29, 29 December 2009 (UTC)

acylation of benzene rings with amino acids

I was told Friedel Crafts acylation would be too harsh of a reaction to do amino acid acylation cleanly (there would be lots of polymerisation), even with the amino group protonated. Are there any alternatives or modifications? A superacid to ensure the proton stays on the amino group? Do I have to protect the amino group? Use thionyl chloride or oxalyl chloride instead of PCl5? (This is in-situ acyl chloride formation.) Use an activated ester? Any help would be appreciated.

Do protonated amines react with acyl chlorides even in protonated form? (A second-order reaction?) Or does the proton momentarily come off, with small amounts of reactive free amine reacting with the acyl chloride at any one time? John Riemann Soong (talk) 16:49, 24 December 2009 (UTC)

"Amine + acyl chloride → amide" is often done using glacial acetic acid as solvent. The amine is mostly protonated under these conditions (aids solubility). And the byproduct is HCl, which pushes that acid/base equilibrium even further towards the protonated state, yet the reaction still runs to completion without a problem. DMacks (talk) 05:30, 28 December 2009 (UTC)

Is salt a spice?

Another site, I was reading, it described salt as a "cheap and abundant spice". Is salt a spice?--Idun90 (talk) 17:43, 24 December 2009 (UTC)

Not according to our spice article: "A spice is a dried seed, fruit, root, bark, leaf, or vegetative substance used in nutritionally insignificant quantities as a food additive for the purpose of flavour, colour, or as a preservative that kills harmful bacteria or prevents their growth." Dismas|^(talk) 17:57, 24 December 2009 (UTC)

Salt is not a spice, but it is a seasoning. People often confuse the two terms, but culinarily speaking they are seperate categories of flavorings. --Jayron32 18:15, 24 December 2009 (UTC)

Would this work to generate (small amounts of) electricity?

A bowl-shaped induction coil with a spherical neodymium magnet, suspended so that the whole thing could swing in the wind...or would the effect of having a free-moving magnet flipping pole-over-pole along the coil basically negate any gains? FWIW, I'm not talking about any gains larger than charging a small capacitor and lighting a single LED (as a proof of concept for a fun project). Thanks in advance. --Kickstart70TC 18:04, 24 December 2009 (UTC)

You would have to make sure the bowl moved, and not the magnet, or the magnet and not the bowl. If both moved together nothing would happen. But otherwise, yes. But you'll have to deal with random voltages and polarities. Use a Bridge rectifier. You'll have best results if you can move the magnet perpendicular to the direction of winding (i.e. across the coils), and not left/right along the length of each winding. So if are using wind, and it's shaking left right, lay the coils on the side. I'm not sure if there is a winding that will let you collect energy from motion in any direction. Ariel. (talk) 18:20, 24 December 2009 (UTC)

Thanks, that helps. --Kickstart70TC 18:50, 24 December 2009 (UTC)

The faster the relative motion, the stronger the magnet, and the more turns in the coil,then the greater the voltage, other things being equal. An iron core in the coil might be better able to generate a useful output. If the magnet is made to vibrate rapidly by some fluttering action that might help to get some voltage out. I've seen a novelty which had a magnet on a spring next to a coil. The spring got bent to one side to a release point, after which it snapped back and vibrated fast for a fraction of a second next to the coil, generating a painful output voltage. Not sure why the magnet in your idea is going to flip pole over pole, from your description, without some sort of blades to catch the wind and turn the magnet. The rectifier mentioned above is needed because a magnet moving toward and away from a coil, or rotating next to a coil, will generate AC rather than DC. The rectifier would decrease the output voltage by a fraction of a volt, a potential problem if only a tiny voltage is generated. Other generators use a mechanical commutator, but it's hard to see how one would work with a magnet just wobbling around suspended in a bowl shaped coil. If current were coming out of the coil to a load, or to charge the capacitor and light the LED, that would tend to oppose the motion of the magnet. Edison (talk) 00:16, 25 December 2009 (UTC)

Any downsides to eating lots of sugar-free candy?

Are there any bad effects of eating lots of sugar-free candy over the holidays? --70.167.58.6 (talk) 18:34, 24 December 2009 (UTC)

Well, if it was the only thing you ate, you would die from lack of nutrients.Abce2|Free lemonadeonly 25 cents! 18:36, 24 December 2009 (UTC)

There is some research that shows that eating sugar free foods messes with your bodies sense of fullness. i.e. the body no longer knows how to calculate how many calories you ate based on the taste. It's expecting calories based on the taste, but none showed up. So when you eat other foods you will eat more, since it thinks the tongue "calibration" is off. Eating sugar free foods may therefor cause you to gain weight. This is not a settled issue though, for all I know it could have been refuted, I'm going from something I remember. Also, some kinds of fake sugars can cause diarrhea and other effects - you would have to ask about the specific fake sugar you are eating. Ariel. (talk) 19:15, 24 December 2009 (UTC)

Not to mention that the larger the quantity of certain sweeteners (sorbitol, other polyalcohol sugars, sucralose, etc.) the likelier that diarrhea will result. The polyalcohol sugars (mannitol, sorbitol, xylitol) are often used in candy, and in addition to causing osmotic diarrhea when eaten in large quantity can actually raise blood sugar, an issue for diabetics. Not so merry. So some moderation is advisable. - Nunh-huh 19:23, 24 December 2009 (UTC)

As mentioned at Sugar substitute#Sugar substitute health issues & [6], there have been fears of artificial sweeteners being partially carcogenic, but as the evidence has accumulated most initial concerns have reduced. Some countries have banned some which others have not. There is of course a chance that some risks have not been detected yet particularly for new ones although most are usually tested fairly extensively before release AFAIK. And of note, this applies to a lot of substances in sweets and other things you eat and even if the substance is not new it doesn't mean any increased risk would have been picked up yet and significantly many relatively new substances are not well tested if they are 'natural' Nil Einne (talk) 10:39, 25 December 2009 (UTC)

Gene Therapy

Would it be possible today or sometime in the future for gene therapy to turn off cancer cells (tumor making genes) throughout the entire body? Or can gene therapy only work in one designated part of the body, i.e the eyes? —Preceding unsigned comment added by 71.156.64.184 (talk) 18:46, 24 December 2009 (UTC)

It sounds possible, but we can't do it yet. It will probably need different therapies for different cancers since it is different genes that need turning off (or on), though. There was some work published recently sequencing cancer cell DNA which should help with the development of such gene therapies. --Tango (talk) 19:05, 24 December 2009 (UTC)

I think we just had this question. DRosenbach ^{(Talk | Contribs)} 04:47, 25 December 2009 (UTC)

easily transported survival rations

In terms of pure survival it appears that 40 grams powdered potatoes, 15 grams powdered milk and 17.76 grams milled flax seed mixed with water and consumed six times per day along with a daily multiple vitamin tablet is sufficient to provide a balanced diet that includes fiber. How long can such a diet sustain human life without alternate or additional ingredients? 71.100.6.153 (talk) 19:21, 24 December 2009 (UTC)

I'm not completely convinced we know about all the microneutrients, but you should read total parenteral nutrition. Are you sure you are getting enough minerals like magnesium? What about EFAs? Did you check that your proteins were complete? Also, the nutrition numbers for foods is not exact - there is a wide variation in real food. You would be in trouble if you happened to have a batch will less of some mineral or other. Ariel. (talk) 19:28, 24 December 2009 (UTC)

Did you check the nutritional content of each of these, noting the total against the recommended daily allowances of all essential nutrients? The info is likely to be on the food packaging. There is more to nutrition than carbs, protein, fat and fiber. Would your diet supply all needed vitamins and minerals? To survive for a week or 2 on such a diet might be less of a challenge than to stave off pellegra, scurvy, beriberi or other deficiency disease over months or years. Would your diet provide much fat? Not if it were nonfat milk. Fat has 9 calories per gram compared to 4 per gram for carbs or protein, and something with some fat content would seem to be a desirable calorie dense part of survival rations, especially if weight is a consideration and any climbing, hiking or hard work is to be done. A very boring diet might dampen spirits, not the best thing when a good attitude could aid survival, which is an argument for variety. Edison (talk) 19:37, 24 December 2009 (UTC)

I don't see any salt in that diet either - that would be a problem sooner than anything else. Salt, water and sugar would probably do for a few weeks (although you wouldn't feel too good). If you've got some decent fat reserves on your body then you could do without the sugar, too. --Tango (talk) 19:55, 24 December 2009 (UTC)

I understand that the modern thinking is that the optimum amount of salt required is very low, and salt will be in the ingrediants naturally anyway. The recommended daily amounts are achievable goals in salt intake reduction, and not the optimum. I don't think any nutritionist has regarded sugar as an essential nutrient for several decades at least. 89.240.110.255 (talk) 16:11, 26 December 2009 (UTC)

I should have made clear that minerals are generally included in a daily vitamin supplement tablet and that one reason the Irish came to depend so heavily on the potato is that with milk it provides all of the amino acids. So much so in fact that a computer program picked potato and milk combination over egg white. What I am thinking of here is minimum transport weight to disaster areas of maximum nutritional benefit. 71.100.6.153 (talk) 20:33, 24 December 2009 (UTC)

A kilogram of fat would provide 9000 calories, while a kg of the instant mashed potatoes I found in the kitchen would provide only 3928 calories. A kg of the ground flaxseed I found in my kitchen would provide 5714 calories (they have 80 calories per 14g serving, and 45 of the calories are from fat, along with 4 g of fiber. Using data for nonfat dry milk from [7], it has 3600 calories per kg. One ration portion as you described it above, per the figures I found, would provide 157 calories from potatoes, 54 from milk, and 102 from flax, for 313 calories per each of the 6 meals, or 1878 per day. Why would the food providers want to give people 6 tiny meals a day, with all the attendant lining up and washing up? I also think the recipients might riot after 4 days of mashed potatoes 3 (or 6) times a day. Some variety would seem highly desirable, rather than just looking at maximum nutrient density. Unappetizing food might be rejected even by the malnourished. I read of stranded travelers who were fed macaroni and cheese (liked well enough by most folks) 3 meals a day for a week who came to loathe the idea of ever eating it again. A factory in town was manufacturing the product and donating it to the shelter where the travelers were staying. Edison (talk) 00:06, 25 December 2009 (UTC)

I have no problem with developing a very long list of powdered ingredient combinations and hopefully such a list already exists. Chocolate as a matter of fact was used by the Inca for this very purpose and there are many powders to work with including rice and soy powder. The key is the right amount of each ingredient in one batch for each combination to be divided into three meals or six meals per day. 71.100.6.153 (talk) 11:40, 25 December 2009 (UTC)

OK the calories may suffice if you don't move too much. Proteins have all needed amino acids as you point out. However, I think you won't get enough proteins: powdered potatoes have about 10 per cent, and powdered milk about 15 per cent proteins. That will get you all in all 24g plus 14g = 38g protein per day. This is too low, if you believe the rule of 1g/kg body weight per day for normal people, and 1,5g/kg for athletes. --Ayacop (talk) 16:35, 25 December 2009 (UTC)

Below is the result after adding other food sources...

Notice that in this case the program picked egg white and potatoes but added a taste of canned vegetables and about a cup of flax seed. Since potato is considered first and filled the requirement for carbs there was no need to include soy powder or rice as when potato is not included.

'	1 - 290 calorie meal	'	'	'	'	'	'	'	'
	potatoes	milk	chicken	flax	c veg	egg w	soy	rice	raisins
Servings	2.150625	0	0	1.48	0.1271875	0.470208333	0	0	0
Grams	45.163125	0	0	17.76	1.271875	5.6425	0	0	0

71.100.6.153 (talk) 04:08, 26 December 2009 (UTC)

trying to find out about a plant I saw in Mexico

I'd like to attach a picture of a plant I saw in Baja, Mexico. I think it may be a palm, rather than a cactus. Can I attach a picture? —Preceding unsigned comment added by Jeancahill (talk • contribs) 19:30, 24 December 2009 (UTC)

Assuming you have the rights to the picture (ie you took it yourself) you will need to upload it to Commons before you can post it on this page. Brand new users do not have the ability to upload directly to Wikipedia but Commons is just as good, pictures there can be displayed on Wikipedia pages (or any other Wikimedia project). SpinningSpark 20:50, 24 December 2009 (UTC)

The alternative is to upload it to Flickr or Imageshack or Photobucket or something similar, and post a link here. Tevildo (talk) 22:25, 24 December 2009 (UTC)

what's with the weird alkynyl-cyclopropane group in Efavirenz?

What is its purpose? Does it get metabolised to something else in the body? John Riemann Soong (talk) 22:02, 24 December 2009 (UTC)

I don't know, but I don't think it is metabolised. If you look at the structure-activity relationships of other drugs, such as opioids, then you will also see these alkynyl/cycloalkyl groups in the antagonists (compare nalorphine to morphine; also see naltrexone, naloxone, naltrindole, nalmefene). Here is a ref speculating why those functional groups produce antagonistic effects, and it thinks that it may prevent G-protein coupling to the receptor, so it would be wrong to extrapolate that to enzyme inhibition (as is the case with your ligand). --Mark PEA (talk) 22:18, 24 December 2009 (UTC)

December 25

Holes in sandstone

We have several steps made out of large sandstone slabs. They are nearly flat and essentially oblong. They measure approximately 48"x30"x10". Two of them have many small holes in the top and one edge. These holes vary slightly in size but each one is approximately 5mmx5mm. Each hole is quite round and has straight sides and a nearly flat bottom. I am puzzled as to what might have produced these holes. They do not appear to be man made and they are random in their distribution. There are several hundred holes in each slab. The stones are uncut. They were lifted from their original site with a forklift and transported by truck. Does anybody have a clue as to what might have caused these holes? —Preceding unsigned comment added by 98.149.248.148 (talk) 00:29, 25 December 2009 (UTC)

Drilling a series of holes and then inserting a wedge to fracture it is a common method of quarrying stone blocks, but this does not sound like what you have. It is probably the fossil holes of a species of Skolithos. SpinningSpark 01:51, 25 December 2009 (UTC)

Marine life and decompression sickness

Is marine life affected by decompression sickness? As far as I can tell from skimming the Wikipedia article on decompression sickness, it only talks about humans and doesn't say anything about other life forms, and it probably should at least make some mention of how or if it affects other life. —Lowellian (reply) 00:58, 25 December 2009 (UTC)

Sperm whale bones show pitting which is likely a result of decompression sickness. --Dr Dima (talk) 01:39, 25 December 2009 (UTC)

I think we just had this question. DRosenbach ^{(Talk | Contribs)} 04:46, 25 December 2009 (UTC)

We did, on the Reference Desk? Could you provide a link? And if there's information, could someone please add it to the "decompression sickness" article? If that article actually had any information on non-humans, then I and others wouldn't have to ask here. —Lowellian (reply) 05:36, 25 December 2009 (UTC)

I don't recall this question being asked before, and I could not find it in the archives. There was a more general question about respiratory system of marine mammals, here; but not this specific question AFAIR. Yes, I think it may be a good idea to add a cross-link from the decompression sickness article to the sperm whale article. By the way, quick Google Scholar search came up with this paper describing lesions indicative of decompression sickness in a few more species of marine mammals. --Dr Dima (talk) 06:33, 25 December 2009 (UTC)

See, this doesn't make sense to me: if cetaceans suffer from decompression sickness, wouldn't that severely inhibit their ability to dive and surface (especially since they may have to rapidly in order to hunt or breathe)?

—Lowellian (reply) 11:25, 25 December 2009 (UTC)

There is a lot in the literature which is pinning the blame for decrompression sickness in whales, especially beaked whales but also other species, on naval sonar.[8][9][10] The whale's normal diving behaviour is designed to avoid, or at least keep under control, the effects of decompression. It seems this is disrupted by sonar as the whales attempt to avoid the sonar signals and has led to beachings. On the other hand, the pitting of the bones mentioned above may be normal for whales and does not necessarily indicate that the animal was sick (although it would for a human). SpinningSpark 14:41, 25 December 2009 (UTC)

I think DRosenbach was referring to Wikipedia:Reference desk/Archives/Science/2009 November 27#Deep sea fish: do we know how the buggers cope with the insane pressures? which touched on this issue somewhat Nil Einne (talk) 15:16, 25 December 2009 (UTC)

And what about non-mammalian marine life? Fish? Crustaceans? Other invertebrates?

—Lowellian (reply) 11:25, 25 December 2009 (UTC)

Non-mammal marine life does not normally need to surface in order to breathe. This implies that they do not need to rapidly and regularly surface. This may also imply that they have less molecular nitrogen dissolved in their blood. Therefore, under normal conditions, decompression sickness should not be an issue for non-mammal marine animals. Under abnormal conditions - being pulled to the surface from the depth of hundreds of meters - deep sea fauna does not fare very well at all :( --Dr Dima (talk) 01:18, 26 December 2009 (UTC)

Read recently that many abyssal fish die from hyperthermia not decompression sickness, they are used to a single cold water temperature and if put in water of that temperature they dont die. I looked for a ref but couldn't find it. Polypipe Wrangler (talk) 12:43, 26 December 2009 (UTC)

Is this real?

http://www.viddler.com/explore/failblog/videos/211/

That building seems awfully too strong. --99.237.234.104 (talk) 06:42, 25 December 2009 (UTC)

It is at Cankiri in Turkey and has been widely reported including by the BBC so appears to be real. SpinningSpark 11:02, 25 December 2009 (UTC)

The building survived the 1999 Izmit earthquake, where many other older building were flattened. However I'm not sure what the effects were in Cankiri Province specifically. ~AH1^(TCU) 02:52, 26 December 2009 (UTC)

Well that was interesting video! SPOILER ALERT! For anyone who hasnt't see it the building actually rolled over onto it's roof rather than collapsing!! Kudos to the builders, how many structures built today would be able to hold together like that? Now, did they eventually manage to demolish the (now upside down!) structure? What sort of construction, was it, re-inforced concrete slab?--220.101.28.25 (talk) 11:56, 26 December 2009 (UTC)

Viscous flow of granite

Viscosity, Rheid, Granite. I'm kind-of-confused. I thought granite was a fairly solid rock and that if you pushed on it then it would snap. Rheid suggests that it flows in a viscous manner. Is that really the case? How does this stuff work? -- SGBailey (talk) 09:09, 25 December 2009 (UTC)

The first sentence of our article says "Almost any type of rock can behave as a rheid under appropriate conditions of temperature and pressure." I think you are correct about the behaviour of cold granite, but perhaps you should wait for a Geologist to give an authoritative reply after their Christmas festivities. Happy Christmas! Dbfirs 09:51, 25 December 2009 (UTC)

Yet Rheid suggests granite flows at STP -- SGBailey (talk) 10:04, 25 December 2009 (UTC)

Yes was about to point that out. Specifically "Granite has a measured viscosity at standard temperature and pressure of ~4.5 • 1019 Pa·s [1] so it should be considered a rheid". BTW Christmas is over in 16 minutes Nil Einne (talk) 23:44, 25 December 2009 (NZDT; UTC+13)

boot polish SpinningSpark 11:10, 25 December 2009 (UTC)

On further thought, if granite snaps then it's clearly quite inelastic. Remember rheid "is a solid material that deforms by viscous flow. To be considered a rheid, deformation by flow should exceed elastic deformation by at least a factor of three." Something that snaps could easily have deformation by flow exceeding elastic deformation by a factor of 3 I guess. Something like elastic or a rubber band (or basically anything made from vulcanised rubber for example) which obviously has great elastic deformation clearly does not. Remember glass clearly shows viscous flow even if the examples commonly used like old stained glass windows are bullshit. Whether it's rheid, I don't know but I guess it isn't something commonly considered since glass is probably of limited interest to geologists Nil Einne (talk) 23:50, 25 December 2009 (NZDT; UTC+13)

There are two contrasting types of behaviour, brittle-elastic and plastic (or ductile if you will). Which behaviour dominates in a material depends on three main factors - temperature , increased temperature promotes plasticity - confining pressure (the weight of overlying rock - i.e. how deeply it's buried), increased confining pressure suppresses brittle behaviour and the rate of the applied deformation, or strain rate, high strain rates lead to more brittle and low strain-rates to more plastic behaviour. As an example of contrasting properties depending on physical conditions, rock salt is a brittle elastic solid at surface temperatures unless it is wet, when it flows plastically such as in the salt glaciers of Iran, that move only in the wet season. Granite has been observed to deform plastically under bending (but at very low strain-rate) in a classic series of long-term experiments (decades) in Japan[11]. Mikenorton (talk) 13:09, 25 December 2009 (UTC)

Keeping people alive on Xmas day

I was reflecting on the fact that it is quite sad for people to die on Xmas day (of course it is sad that they die at all, but it just seems that bit worse for the families). This got me to wondering whether there is any way to keep people alive for a few more days (or even hours) with any kind of extreme medical intervention. I am thinking of people who die of natural causes, and who are reached by medical personnel quickly but who, regardless of treatment, would die very quickly anyway. I am imagining something like giving them large, ongoing shots of adrenalin, or other time of extreme intervention. Of couse, no body would ever do this, at least not as a usual course of action, but I am just wondering what is possible. PaulRicks1983 (talk) 14:26, 25 December 2009 (UTC)

It depends what you mean and what's the cause of the person dying (natural causes is a very broad concept). What some consider 'extreme medical intervention' are used all the time, e.g. medical ventilator, feeding tubes, artificial pacemakers, defibrillator and other life support measures. These would be of some use in some 'natural causes' cases but may not be used if it's expected there's no chance the person will live. It also depends on what you mean by dead. These measures may keep the body alive, but if the person is already brain dead then in reality all you have is a living body and while that understably be comforting to many, others may say the person is already dead even if they aren't clinically or legally considered dead. Further, as I understand it from TV shows (not a good source but this also not a good source suggests a similar thing [12]) and makes sense I guess that if CPR is being performed the time you stop may be counted as the time of death. Clearly you could go on for ever in the shows you do see them going on for too long (e.g. 40 minutes) or arguing over whether to stop (or even once I think waiting for the family to arrive although it's probably rarely this extreme in real life) but if you take it to an even further extreme, after a while the body is going to go cold and will eventually even start to rot. In other words, you can't say this person is 'alive' in any meaningful way. Incidentally, I'm not sure whether it would be much worse on the families for many of those in e.g. India, China. Even in places where Christmas is widely celebrated in some form, I don't think it'll necessarily be worse then other times, in fact it may be better. Particularly if happens late in the day and the person has already seen many of their families and friends. Or if it's not an instantenous death, family & friends might be more likely to be able to reach the person before death which can help in many cases. P.S. If we include things like cancer, there are of course a variety of measures which in some instances are very unlikely to elimate the cancer and therefore give the chance of a 'normal life' but which may prolong life by weeks, months or days (usually with some side effects i.e. the whole quality vs quantity thing). Nil Einne (talk) 15:53, 25 December 2009 (UTC)

Caution: a whole load of OR follows. It seems to me, and has been confirmed by my sister in law who's a nurse, that many terminally ill people hang on to die after a holiday or a special event. I'm pretty sure I saw some research a couple of years ago which seemed to back this up, but I have no idea where or what. If someone who's bored on this holiday would like to find it for me then be my guest. (I've got family coming tomorrow and so won't have time.) --TammyMoet (talk) 20:06, 25 December 2009 (UTC)

Purely anecdotal: On a Craigslist forum someone lost his mother to a blood infection from an acute kidney problem problem early this morning. She had hung on for a day or two. More scientifically, I remember reading that despite common belief, people die at a slightly higher rate during holidays due to perhaps an extended time it takes to take care of them. 67.243.1.21 (talk) 01:05, 26 December 2009 (UTC)

I seem to recall a certain episode of M*A*S*H that involves a soldier dying shortly before midnight on Christmas and the subsequent faking of the death certificate to say December 26 instead. This seems like a much easier way to "accomplish" this. 75.157.57.12 (talk) 01:32, 26 December 2009 (UTC)

The Edgar Allen Poe short story, "The Facts in the Case of M. Valdemar" is about a doctor who puts a dying man in a trance as he takes his final breaths. Ideas that human lives can be prolonged meaningfully this way, by Cryonics or by injecting adrenalin (Epinephrine) are all silly. See the article Death. The OP might consider medical personnel whose daily response is to actual needs rather than indulging in a sentimental attachment to a particular holiday. A subsidiary question is whether one has to be sick to die naturally (can one die healthy?). Cuddlyable3 (talk) 02:37, 26 December 2009 (UTC)

Wind mill & water turbine

is it possible to synchronize and combine the mechanical output of wind mill and water turbine and then use it for power genenration? —Preceding unsigned comment added by 203.175.69.210 (talk) 15:10, 25 December 2009 (UTC)

I have given your question a seperate header as suggested in the instructions at the top so that it won't be lost, ignored or distracted from the earlier question. Nil Einne (talk) 15:21, 25 December 2009 (UTC)

Since both output is rotational energy, sure, you can put both axes together in reverse (say by making one axis hollow), and then you have both rotational movements added, i.e., the outer rotation is both rotations added with respect to the inner axis. An application would be to fix a drill bit to one rotating axis, and fix the object to be drilled on the other axis, then lead them together so that their rotation is mutually reverse. --Ayacop (talk) 16:19, 25 December 2009 (UTC)

Did you not like the last answer you got to this question? SpinningSpark 19:27, 25 December 2009 (UTC)

It seems straightforward, even though waterwheel output is steady while wind is highly variable. The waterwheel can have its output controlled by the water inlet valve. The windmill can have its output controlled by varying the pitch of the propellor blades. If the wind stops or drops too low, then there would have to be a clutch to disconnect it so the waterwheel does not drive it like a fan. The output of the waterwheel should be continous and uninterrupted as long as the water level does not drop too low. But why would anyone want to combine them mechanically? For many years hydro generators and wind generators have been connected electrically via the power grid. The first such interconnect was at least as far back as the 1940's, and is quite common today, with photovoltaic also electrically synchronized via inverters. See Electrical grid, Sustainable energy. I've seen a mechanical synchronizer from a hydro turbine to maintain constant speed via a pair of rubber cones which were moved together and apart to adjust the gearing continuously. A clutch would still be needed, or the propellor could be adjusted so the blades are flat (no wind moved by propellor rotation) when they spin like a fan, the opposite of feathering the props in high wind, to reduce the energy waste when the wind drops. Edison (talk) 01:51, 26 December 2009 (UTC)

Attach both machines to a Differential gear. They can then spin at different rates, and you can harvest power from both (or one). Ariel. (talk) 02:00, 27 December 2009 (UTC)

Relativistic mechanical reactionless drive?

Supposing two small neutron stars could be spun to relativistic speeds using enormous magnetic stirrers. If one neutron star/stirrer transferred all its spin to the other stirrer/star via a rod with an epicyclic reverse reduction gear, the stationary star would have less mass (due to relativistic effects) and could be rotated around the spinning star. The process could be reversed, leading to linear motion in space without reaction, in violation of Newtons Third Law of motion.The reverse reduction gear would stop the whole system from spinning and canceling out the effect. I hope. Incidentally, could this work using gyroscopic effects alone in a normal mechanical system working at non-relativistic speeds? 80.0.105.148 (talk) 15:32, 25 December 2009 (UTC)[Trevor Loughlin]

"the stationary star would have less mass (due to relativistic effects)" - how does this happen? Why would it have less mass? First you say you have a stirrer, next the star is the stirrer? Which is it? What's a reverse reduction gear? What process can be reversed? Linear motion, after spinning? I think you are assuming you have a place to "attach" the stars to. You don't. If you try to transfer spin from one star to another using a gear, it won't do that - they whole system will spin instead, because you have no place to attach your gear, and the star is not attached to anything either. Ariel. (talk) 19:49, 25 December 2009 (UTC)

For gyroscopes see Eric Laithwaite and Reactionless drive. 78.151.96.82 (talk) 20:21, 25 December 2009 (UTC)

can't do it. Dauto (talk) 00:44, 26 December 2009 (UTC)

Stopping the star would cause the whole assembly to spin, but then the other star would be spun up in the opposite direction, which would stop this. In any case the spin of the whole system (a long tube surrounding both stars at each end) would be vertical so this would not move the center of mass, merely spin the tube. When the less massive stationary star is made to orbit the more massive spinning star in the horizontal direction, the center of mass will change and the process can be repeated. However, this is all based on the idea that a star becomes heavier when it spins at relativistic speeds. Einsteins theory says that mass increases at near light speed. So an increase in rotational speed to relativistic speeds of part of a system will alter the systems center of gravity? Or am I misinterpreting the meaning of mass when applied to relativity? incidentally it could just as well be a flywheel rather than a neutron star, but in reality only an object made of degenerate matter would stay in one piece at such speeds.—Preceding unsigned comment added by 80.0.102.45 (talk) 13:17, 27 December 2009 (UTC)

I think I see what you're getting at - transferring angular momentum from one star to the other will increase the mass of the accelerated star, and move the position of the centre of mass of the system as a whole. There's no need to use relativistic effects to do this - you could just use two tanks of water with a pump between them, and move the position of the centre of mass by pumping water from one tank to the other. The system will indeed move with respect to its centre of mass, and the speed and radius of its overall rotation will change - but, with no external force applied, the centre of mass won't move with respect to the surrounding space. Tevildo (talk) 15:10, 27 December 2009 (UTC)

You might get linear motion, but it would be oscillatory. The stars would just oscillate relative to their stationary centre of mass, nothing more. --Tango (talk) 15:16, 27 December 2009 (UTC)

I think the crucial point that you are missing is the transfer of energy from one star to the other. If e. g. it is done with an electric generator and an electric motor then the electromagnetic fields carry mass-energy as they move along the tube (or gain energy at one end and lose energy at the other end) - and I'm quite sure that during that process the star which is spun up will move towards the center of gravity. Icek (talk) 08:31, 28 December 2009 (UTC)

Then forget about relativistic effects and neutron stars and instead imagine an old fashioned reel to reel tape recorder in outer space, and assume the tape is extremely heavy,perhaps incorporating lead weights all the way along its length,and there is another reel to reel backing on to it as a mirror image, winding in tape in the same direction. Will the system move whilst it is doing this or stay in the same place? Answer this question before I continue.

                                   o_____o
                                    _____  ----> both tapes wound in the same direction.
                                   o     o  —Preceding unsigned comment added by 80.2.207.220 (talk) 13:03, 28 December 2009 (UTC) 

Yes, the heavier star/tape reel will move towards the centre of gravity. However, the centre of gravity _won't_ move unless an external force is applied. You can move the system as a whole around its centre of gravity (and not violate Newton's Third Law - the force needed to move the system is reacted against the motor which drives the tape, in your second example), but you can't move the centre of gravity itself. Tevildo (talk) 13:55, 28 December 2009 (UTC)

Unofficial battery charger

I recently lost the charger to my Nintendo DS and my mother bought me a new one - which can charge a DS, DS Lite or PSP - made by a company called "Quick Act". Now, I know that over time, any battery will gradually wear out and won't last as long as when it was new, no matter how well it's taken care of. My question is, would using an unofficial charger exacerbate this problem? Would the battery run down faster using a poor-quality charger (it's safe to assume it's poor-quality since my mother bought it...) in comparison to the (presumably high-quality) official charger? Vimescarrot (talk) 15:37, 25 December 2009 (UTC)

There are two problems you can get with cheap chargers. The first is overcharging, which will definitely shorten the battery life if you leave the batteries connected for too long. A good charger will change to trickle charge when the batteries are getting near full charge. If your charger does not do this you must make sure it is only left charging for the prescribed time. The second problem is that some chargers (in order to avoid the first problem and to make them even cheaper because they do not have to deliver high currents) only work as trickle chargers and will take longer to charge the batteries than it takes to discharge them in operation. No idea what you have got - read the instructions :) SpinningSpark 19:35, 25 December 2009 (UTC)

What Spinningspark said. :) It's also possible, however, that the charging circuit is actually in the DS itself, and all the "charger" does is to provide power to it - this is the situation with mobile phones. In this case, the "quality" of the charger doesn't matter, as it's just providing fixed DC. See also Battery charger and Lithium-ion battery for more details. Tevildo (talk) 22:01, 25 December 2009 (UTC)

Ahh, neat - how might I find out if the DS has such a thing? Vimescarrot (talk) 22:38, 25 December 2009 (UTC)

I don't have a DS myself, but, looking at some pictures, it seems that the charging monitor light is on the DS itself rather than the charger. This would suggest to me that the charging circuit is in the DS. I also note that you can buy "chargers" for £1.75. :) That will barely cover the cost of the _plug_, let alone anything but the most basic circuitry. I've also seen some forum postings that suggest it's possible to recharge the DS by connecting it directly to a USB port. It's not a definitive answer, but... Tevildo (talk) 00:29, 26 December 2009 (UTC)

Hmm. Alrighty, thanks. I think I'll risk it! :p Vimescarrot (talk) 00:39, 26 December 2009 (UTC)

Elements and the three states of matter

Can all naturally occuring elements be heated or frozen into the three basic states of matter? Lova Falk (talk) 17:32, 25 December 2009 (UTC)

Not at atmospheric pressure, but if you can change the pressure then yes, I believe so. --Tango (talk) 17:47, 25 December 2009 (UTC)

To be specific, the ones you can't get at atmospheric pressure are solid helium, liquid carbon, and liquid arsenic. Despite apperances, iodine _does_ liquify at atmospheric pressure. Tevildo (talk) 18:13, 25 December 2009 (UTC)

Thank you! Lova Falk (talk) 18:30, 25 December 2009 (UTC)

Is that it? I would have thought there were more than that. --Tango (talk) 19:02, 25 December 2009 (UTC)

The vast majority of elements are solid metals which can all be melted. SpinningSpark 19:22, 25 December 2009 (UTC)

Incidentally, although the arsenic and sublimation articles say that arsenic sublimes at atmospheric pressure, List of elements by melting point says it doesn't. I'll do some reference checking and make the appropriate corrections. Tevildo (talk) 21:35, 25 December 2009 (UTC)

Done. List of elements by melting point is now correct. Tevildo (talk) 21:51, 25 December 2009 (UTC)

Don't forget the classic example of carbon dioxide, in which a liquid state does not exist until pressures exceed 5.1 atmospheres. ~AH1^(TCU) 02:34, 26 December 2009 (UTC)

True - many substances undergo sublimation at atmospheric pressure. However, carbon and arsenic are the only elements that do so. Tevildo (talk) 02:58, 26 December 2009 (UTC)

El Niño-Southern Oscillation

Hi. When the El Niño warm pool of water cuts off the Humboldt Current during a strong El Nino event (more than 1.5C above normal in the Niño 3.4 region), where does the upwelling of cold water resurface? Does this occur in the Western equatorial and north Pacific, or in the Northeastern Pacific, or in the Southwestern Pacific? Let's say the current is both cut off at the southern end, as well as blocked at the equator, the northern coast (Peru-Chile border), and from the west, as it is now[13], where does it resurface, or does it have significant effects on the global Thermohaline circulation? Thanks. ~AH1^(TCU) 18:14, 25 December 2009 (UTC)

Fires in the Amazon rainforest and ENSO

This is a related question to my original one. In which years were forest fire activity higher than normal, due to higher-than-average temperatures and drought (and possibly other factors such as lightning, arson, and slash-and-burn)? Was El Nino present in those years, as it was in 2002 and 1997, when forest fires threatened forests and peat bogs in Borneo? ~AH1^(TCU) 03:23, 26 December 2009 (UTC)

replacing -COOH with -CH3

How would I approach this? I was thinking reduction .... use lithium aluminum hydride then proceed to elimination, forming an alkene that I can then reduce? (The proton is prolly a problem, so I guess use the ester...)

(Also, how is LiAlH4 used in the reduction of protic amides? Even if you use an excess, isn't the formation of anionic amide nucleophile kind of a problem?)

Or maybe, use decarboxylation with some methyl halide in it? (If there's an amine group in the compound, e.g. an amino acid, do I have to protect the amine, or can I just use strongly acidic conditions? Would that inhibit decarboxylation?) It's actually okay if the amino group picks up a methyl group, but two methyl groups would be bad. Help??? John Riemann Soong (talk) 18:26, 25 December 2009 (UTC)

Anyone? I know decarboxylation is a step required for methyltransferase to work... any way of duplicating the same idea in vitro? John Riemann Soong (talk) 06:08, 26 December 2009 (UTC)

Reduction of a carboxylic acid with LAH would work fine...the first equivalent of hydride does react with the acidic proton, but LAH is a strong enough reducing agent to reduce that carboxylate. But given your alternative is decarboxyliation, your whole scenario is not well-formed...one way shortens the carbon chain, one does not. You'll need to ask specific, well-explained situations rather than vague ideas...given your history here, you'd better know that the devil is in the details and the details you leave out are the ones that cause you trouble later! DMacks (talk) 04:01, 28 December 2009 (UTC)

This involves reduction of amino acids. (I'm using the skeleton of the amino acids as building blocks for larger compounds, but the COOH group is in the way.) What's the most feasible/practical way of going about this? I was thinking doing a low-temp reduction with DiBalH, stopping at the aldehyde and then reducing further with Clemmensen. (Generally, Clemmensen is cheaper / less messy than Wolf-Kishner, right? Or is W-K easier to work up since the waste product is N2?)

Are there any enzyme complexes (that would work in vitro) that would transform COOH to CH3? I was thinking decarboxylation effectively creates a carbanion nucleophile, which would go on to attack an alkyl halide ... but prolly quite problematic with an amino group? Also, is there any way to encourage monosubstituted product? John Riemann Soong (talk) 04:40, 28 December 2009 (UTC)

Decarboxylation/methylation is incredibly difficult to control. N-alkylation, loss of stereochemistry, etc., and even very difficult to decarboxylate at all unless the carbanion is stabilized. You're safer and saner to just reduce the COOH to CH3. Generally, both W-K and Clemmensen are messy—extreme acid or base, possible use of mercury or high-temperature—you have to decide what your substrate can tolerate (if either). And the success of Dibal reduction that is controlled enough to stop at the aldehyde is substrate-dependent—"looks great on paper". There are lots of ways of reducing alcohols to alkanes (deoxygenation via radical reactions is especially popular there...several "name reactions" for several variations). Lots of people like to use a tool called "google" to look up information...you can type in a phrase and it will give you some references (and even try to find something close if there is no exact hit). For example, "reduce carboxylic acid to methyl" first result is exactly what you want. DMacks (talk) 05:08, 28 December 2009 (UTC)

I did google it .... but I used abbreviations. Oh hmm. John Riemann Soong (talk) 05:26, 28 December 2009 (UTC)

Attaching a light to a wall

Hi. I have a light that I need to attach to an interior wall (the wall is painted plaster, no wallpaper). The light probably weighs about 500g. Because I am living in rented accomodation I cannot drill into the wall (even if I agree to laster fix it), so I need a way to fix it to the wall without damaging the wall or the paint. I imagined that there would be some kind of "sticky pad" that would hold the weight but allow itself to be peeled away eventually, but I have tried all kinds of Google searches and searches on shopping sites but can't find anything matching that description. Could anybody please recommend how I could attach this light? Thanks StickyProblem (talk) 18:32, 25 December 2009 (UTC)

Yes, you can buy various double-sided tapes, self-adhesive Velcro and "adhesive foam pads" (try a Google search) which are possibly strongest, but you should be advised that any such method of fixing may not be suitable for heavy electrical fittings because, however strong the adhesive, the painted surface of the wall may not have the equivalent strength. Dbfirs 19:52, 25 December 2009 (UTC)

To hold 500g you will need a very big pad - that way the weight is spread over lots of paint and it should be fine. --Tango (talk) 20:01, 25 December 2009 (UTC)

Try these: 3M Command Strips Ariel. (talk) 19:54, 25 December 2009 (UTC)

I was thinking some type of suction cup? If the surface is smooth enough --220.101.28.25 (talk) 20:02, 25 December 2009 (UTC)

Wedge a suitably shaped piece of wood ceiling to floor. Attach light to wood. Smaller and lighter the wood the better from an aesthetic viewpoint. Advantage: little to no attaching to the wall. Disadvantage: it looks stupid. Bus stop (talk) 20:11, 25 December 2009 (UTC)

Why did someone delete this contribution? Here it is again: The landlord will not be pleased as the tape will almost certainly damage the surface when removed, particularly if it is tough enough to support 500g. I suggest putting the light on a pole, or asking the landlords permission to pay for an electrician to fit a proper light. Merely sticking it to a wall will be unsafe and dangerous. 78.151.96.82 (talk) 20:07, 25 December 2009 (UTC)

(after edit conflicts) Even on smooth glass, suction cups eventually fall off. If your fitting is low voltage and there is something soft underneath for it to fall on, then Tango's large pad of Ariel's 3M strips (or Foam tape) will do the job, but be aware that when you remove the fitting you might take paint off the wall. Dbfirs 20:26, 25 December 2009 (UTC)

[14] I would guess there was an edit conflict and it didn't inform Tango Nil Einne (talk) 09:17, 26 December 2009 (UTC)

A small screw with a small rawplug is likely to be less unsightly after the light is removed, then a large blemished patch where a large amount of sticky tape was. Safer too. 78.151.96.82 (talk) 21:03, 25 December 2009 (UTC)

The largest 3M Command strips are claimed to be able to support 3.4kg - that's more than six times as much as our OP requires - they also claim not to leave a mark on the wall when they are ultimately removed. This seems by far the most logical solution here. After all, there are only three options:

1. Hang it from the ceiling: Which involves either something adhesive or something with suction or making a hole.
2. Hang it from the wall: Same deal - adhesive, suction or hole.
3. Make a stand so it can be supported from the floor - a table lamp or a taller 'Torchiere' - or BusStop's idea of wedging a piece of wood floor-to-ceiling and bolting the lamp to that.

If the fitting is designed to be wall-mounted then it's likely that neither (1) nor (3) would be acceptable. If we can't make holes in the wall then you're left with adhesive or suction. You need a removable adhesive and IMHO, 3M leads the world in that kind of product - so using their latest gadget makes the most sense. If you wanted to consider suction cups (and presuming the wall is smooth, shiney and flat) then these claim to support up to 10lbs. Personally, I'd go with the 3M gadget.

SteveBaker (talk) 01:29, 26 December 2009 (UTC)

The 3M hooks are widely used as long as the surface is suitable. The adhesive removes by pulling a tab. Wedging a long plank or pilaster from floor to ceiling would be the next best solution. The wiring could be concealed behind the plank or pilaster. The bottom could be trimmed to fit snugly around the baseboard. A pair of wedges could be tapped in to secure it, with a protective pad to protect the ceiling surface. Care is needed to avoid denting the surface by too much pressure. Trim could then be attached to conceal the wedges. I might do this if I were planning to live there a long time. Edison (talk) 03:40, 26 December 2009 (UTC)

As a landlord I have bad experiences with stick-on hooks. I often find many of them - they must be sold in multiple packs - all over the house after the tenants leave, and they always damage the surface when you remove them, requiring the surface to be smoothed and the room to be redecorated. Bear in mind that you will be sticking anything to the paint over the plaster, and not the plaster. In my experience the paint will invariably come off when you remove them, and perhaps even some of the plaster too. 92.24.73.139 (talk) 15:16, 27 December 2009 (UTC)

As a landlord myself (I have one house in the UK and another in the US that are rented out), I suggest you invest in a better grade of paint and plaster! I rarely have this problem in either of the houses I rent out (although I have plenty of other problems with inconsiderate tenants). Besides, these 3M hooks are very new and they say (in an unqualified manner) that they won't damage the surface. If your tenants use these new kinds of hook and the wall suffers then I think it's fair to say that they did 'due diligence' and you should seriously consider whether it's your own fault. However - I doubt very much that you are talking about these new-style 3M hooks - some of the older kinds were indeed likely to damage the wall. SteveBaker (talk) 17:58, 27 December 2009 (UTC)

Gears

How to design a simple gear —Preceding unsigned comment added by 202.162.160.246 (talk) 19:31, 25 December 2009 (UTC)

We're going to need way more detail than that. But, read gear, and all the pages linked to it about various types of gears. Ariel. (talk) 19:50, 25 December 2009 (UTC)

Also, if you plan to design the gear to articulate with another gear (or anything else), you might read gear ratio. Nimur (talk) 23:11, 25 December 2009 (UTC)

A very simple gear is a lantern gear, which is not covered very well in the Gear article, nor does it have its own well deserved article. These were used in early machines from the 1500's, in clocks as well as large machines like windmills and waterwheels. One gear consists of pegs projecting out from a rotating shaft, either radially from the shaft or parallel to the shaft, extending from a disc attached to the shaft. The other gear is a sort of cage, with two discs having between them a series of staves parallel to the shaft the discs are connected to. The rotation of either shaft causes the projecting pegs to engage the staves of the cage. No precise machining of gear teeth is required as for later gear arrangements. You could make one out of dowel rods and plywood. You might be able to make one out of Tinker Toys. Varying gear ratios are had by varying the number of pegs on one shaft versus staves on cage on the other shaft. Here is another version, where the pegs project upward from a disc attached to one shaft, rather than projection radially. This version is illustrated here in a mule powered irrigation system. Here is a modern drawing of a lantern gear driven by wind power to pump water. Here is one from American colonial days, where a water wheel drives a mill. Here is another illustration from 1661. A gear ratio and 90 degree axis change are accomplished. If I recall correctly, Diderot discussed them in his early Encyclopédie in the 1750s. They were commonly used for hundreds of years in machines large and small, and do not require a foundry or precision machine tools. There is likely much more friction than in fancier metal gear teeth. Edison (talk) 01:21, 26 December 2009 (UTC)

Why is Swine flue in decline this winter?

The number of cases in the UK and in the US has been declining this winter. Why is this despite the increasingly cold weather of winter, when a layperson's view would expect things to get worse? 78.151.96.82 (talk) 19:58, 25 December 2009 (UTC)

Because lots of people have already had it and are now immune. There is also lots of Tamiflu (and similar antivirals) and even some vaccines available. The cold weather would tend to increase infection rates (indirectly - it's people spending more time indoors with each other, not the coldness itself that does it) but it seems the opposite effect from increased immunity and drug availability is having a greater effect. --Tango (talk) 20:07, 25 December 2009 (UTC)

I thought that only a small proportion of the population had had it. If that is the case, then immunity would niot be the reason. 78.151.96.82 (talk) 20:15, 25 December 2009 (UTC)

It's a few percent, I think (there are no accurate numbers now since they aren't testing most people). That is enough to make a difference, particularly when you considered things at a more local level where percentages in some areas will be much higher. --Tango (talk) 20:28, 25 December 2009 (UTC)

I have to say I'm doubtful a few percent would make a difference, as then epidemics like the Black Death would never happen. 78.151.96.82 (talk) 21:05, 25 December 2009 (UTC)

A few percent immunity won't prevent an epidemic on its own, but it does make a difference, particularly, as I said, on a small scale. A few percent nationally will mean there are places with very high immunity, which makes a difference. Also, those that are immune will, disproportionately, be those most at risk of getting infected, since they are the most likely to have already been infected. --Tango (talk) 21:57, 25 December 2009 (UTC)

That sounds very unlikely, do you have a source? I believe immunisation programs require a take up rate of 60-80% to be effective. SpinningSpark 23:58, 25 December 2009 (UTC)

For something like smallpox where the aim was to eliminate the disease entirely, you need something like 95%, I think. When you are just trying to reduce the chance of an epidemic, much smaller amounts are useful. To effectively eliminate the chance of an epidemic you need really high rates, but it is still beneficial to reduce the risk even if you don't eliminate it. --Tango (talk) 15:01, 26 December 2009 (UTC)

Another reason could be that many people in developed countries have also had the swine flu vaccine, and are now immune to the virus. Getting the virus once does not give a person complete immunity from swine flu, just as getting the seasonal flu once does not make you immune to it, and there was little natural immunity in the human population to begin with. However, currently the rates of contraction of the virus by month during the year seem similar to the historical H1N1 1918 flu pandemic, only without the high death rate. ~AH1^(TCU) 02:17, 26 December 2009 (UTC)

(edit conflict)Well, first off, Tango said a difference, not an effective one. Second of all, 2009 flu pandemic in the United States says about 1/6 of Americans has potentially contracted it - definitely overly significant, especially when you consider herd immunity. ~ Amory (u • t • c) 02:19, 26 December 2009 (UTC)

It's possible that many more people have had swine flu than the reported figures suggest. There was a news report last week in the UK which claimed that, for most people, swine flu was no worse than a bad cold, and many people in the UK have had bad colds this autumn which could actually have been swine flu - as nobody is being tested except people who are really, really ill with flu symptoms this is speculation. (OR both myself and my husband had symptoms which match those given for swine flu: they weren't bad enough to keep us at home, never mind in bed!) Also the recent cold snap will have killed off many bugs, swine flu included. --TammyMoet (talk) 10:12, 26 December 2009 (UTC)

The key difference in the symptoms between a cold and flu (and swine flu has identical symptoms to other strains of flu) is the fever. Colds don't usually have an associated fever, flu almost always does. If people aren't taking there temperatures then there is no way they can really know what is wrong with them. Also, even those that have definitely had flu could have had any strain - the UK stopped routinely testing to see what strain people had months ago. That means all the numbers are extremely imprecise. I expect that 1/6 figure is an upper estimate - it seems rather higher than I'd expect for a mid-range estimate. --Tango (talk) 14:57, 26 December 2009 (UTC)

It is not a few percent: The U.S. CDC estimates that by the middle of November, 34 million and 67 million Americans had already had it (and around 10,000 had died from it).[15] That is around 10-20% of the U.S. population. About 60 million have been vaccinated[16]. Although there is certainly overlap in the two groups and large error bars on the estimates, as many as 40% of the U.S. could already be immune to it. 75.41.110.200 (talk) 15:04, 26 December 2009 (UTC)

According to the Public Health Agency of Canada[17] and Google Flu Trends[18], the flu epidemic peaked in Canada around the first or second week of November, and has been since on the decline. Since the vaccine was distributed in Canada in late October, it's possible that higher rates of immunity to the virus, as well as the virus being circulated in the vaccine being much less virulent (according to the article, "the virus is first adapted to grow at 25°C and then grown at this temperature until it loses the ability to cause illness in humans, which would require the virus to grow at our normal body temperature of 37°C. Multiple mutations are needed for the virus to grow at cold temperatures, so this process is effectively irreversible and once the virus has lost virulence (become "attenuated"), it will not regain the ability to infect people."). However, the H1N1 flu seems to have become the dominant strain in Canada, as close to 100% of the tested cases were pandemic H1N1 since late October, although total flu activity has now declined to ordinary seasonal levels. ~AH1^(TCU) 19:12, 26 December 2009 (UTC)

Another possibility, though I freely admit it's rampantly cynical, is that the media have moved on to other things. Repeating what's effectively the same story ("some people have had flu, it's a DEADLY NEW STRAIN but there's no need to panic") over and over again doesn't sell newspapers. Tonywalton ^Talk 01:17, 28 December 2009 (UTC)

Color Of Rosiglitazone Maleate (Avandia)

I have seen brown and pink or light pink rosiglitazone maleate (Avandia) tablets. Does this drug come in all white?174.3.102.6 (talk) 23:52, 25 December 2009 (UTC)

According to this, the genuine product (in the UK, at least) will only come in pink 2mg, orange 4mg or brown 8mg tablets, marked "GSK" Glaxo SmithKlein. It's not out-of-patent yet, so nobody can legally manufacture generic equivalents. Does "only get prescription drugs from a real pharmacist using a real prescription that a real doctor has written for you" count as medical advice? I hope not - if it does, though, please can someone delete it? Tevildo (talk) 00:47, 26 December 2009 (UTC)

It's good advice.Cuddlyable3 (talk) 01:32, 26 December 2009 (UTC)

Concur 101% with Cuddlyable3. You don't need a medical degreee or MD registration (I hope) to give bit of old fashioned common-sense. --220.101.28.25 (talk) 05:08, 26 December 2009 (UTC)

December 26

Is galactic red shift not really the Big Bang singularity’s time-dilating effect?

Long ago (in high school) I wanted to be an astrophysicist before circumstances forced me into engineering, but I try to track some of the issues from a layman’s viewpoint. If light heading into a gravity well is blue-shifted (just read this on Wikipedia), and that which is coming out is red-shifted, what else can one make of the red-shift of light from distant galaxies apart from conjecturing an expanding Universe alone? ‘Long ago’ and ‘far away’ mean the same thing, yes? This means that for all practical purposes the Universe from all standpoints is surrounded by its Beginning, which is the Singularity that preceded the Big Bang. Could it not be that the red-shift we see in light from so-called receding galaxies is rather due to the fact that the light is climbing out of a gravity well at whose bottom lies the Singularity? I don’t know what the relation between red-shift and gravitational intensity is, whether it follows the R-squared rule of gravity or not, but I suspect that the Hubble Constant is an outcome of the interplay of this relation and the effects of ‘Singularity Gravity’ (to coin a phrase) on space-time. It is not really so much that the distant galaxies are receding faster and faster as that WE are much farther from the Centre than they are. After all, they are younger than we are as they are closer to the centre. The red-shift we see is ours more than it is theirs. Our spectrometers have departed farther from what they should have been nearer the time of the Big Bang. Of course we are at this distance because the Universe is expanding, but need it be in an accelerated fashion? Coming to think of it, the speed of light must have been changing all the time since the Big Bang – in all neighbourhoods. Either that, or what we now call a metre (meter) has been stretching out as we moved away from the Centre of the Universe….. I have no means of presenting my thoughts in the form of a question as such. I would appreciate a critique of my reasoning so I can see where I can reorient myself. Capping it all is the vexing problem for me of measuring distances to objects that are really in the past. Where are they now? Can we say that because they are still within the light cone then they do exist as we see them until they go over the cosmic event horizon back into the Big Bang black hole? Havanyani (talk) 01:37, 26 December 2009 (UTC)

I cannot answer all of your questions, but why do you think the initial "centre" of the big bang was a black hole? Standard physics expects the speed of light to be constant, but there is a varying speed of light theory that has not acquired much acceptance from the scientific community. Redshift can also be seen in a galaxy within the side that is rotating towards us, but this effect is only noticeable in nearby galaxies. If the universe is infinite, one idea is that the "surface" of the "outside" would have no curve, meaning the universe is flat. However, there's another idea that it could have a negative curve and be "saddle-shaped". This would allow for the "centre" of the big bang to line the "outside" of the curve, but otherwise there is no centre of the universe, and the big bang as an object cannot be located. So there is no "edge" of space, as the visible "horizon" of the visible universe is not the limit of the actual universe itself, although we cannot see beyond that barrier. I'll let someone else answer this before I get too confusing. ~AH1^(TCU) 02:29, 26 December 2009 (UTC)

Not sure I can follow the OP's train of thought, but one thing the OP seems to be grasping at is the fact that gravitational redshift is indistinguisible from motional redshift; that is we cannot tell the difference between gravitational acceleration and other forms of acceleration. Einstein himself called this the Equivalence principle, and it was part of general relativity, which actually deals with MOST of what the OP is talking about. --Jayron32 04:48, 26 December 2009 (UTC)

The act of Sex

Is there a religion in which it is believed and practiced that the act of sex between a male and a female is sacred? 71.100.6.153 (talk) 01:44, 26 December 2009 (UTC)

Quite a few of them, in fact. The LDS Church teaches that sex should only occur between a legally married husband and wife, and that the powers of procreation are sacred and a gift of God. I know many other Christian churches also teach something similar. ···日本穣^? · 投稿 · Talk to Nihonjoe 02:40, 26 December 2009 (UTC)

To take it to an extreme, there have always been cults in the Western world that have had sacred sex. Consider the very cultish Children of God, which openly used prostitution to proselytize new members. See also Sacred prostitution which covers MANY such movements dating back thousands of years through many cultures. --Jayron32 04:39, 26 December 2009 (UTC)

I guess you mean Flirty Fishing, while some of their other (former?) practices involving children are disgusting, I personally find Children of God (cult)#Loving Jesus funny particularly the proscription for males Nil Einne (talk) 08:09, 26 December 2009 (UTC)

"TFI continues to stress the imminent Second Coming of Christ"... Nimur (talk) 12:56, 26 December 2009 (UTC)

If you are are willing to add the word "married" to your question, then Judaism believes so. In fact it is considered one of the holiest acts, because it is the only one that can cause the spiritual (a soul) to be embedded in the physical (the body). Nothing else can do that. (And just like it can be the most holy, it can also be the most un-holy.) Ariel. (talk) 00:26, 27 December 2009 (UTC)

Interesting... perhaps then that is how I should have framed the question, i.e., what criteria makes the act of sex either holy or unholy in various religions? 71.100.6.153 (talk) 01:59, 27 December 2009 (UTC)

Cult leaders often tell their female followers that. 67.243.1.21 (talk) 03:28, 27 December 2009 (UTC)

Mystery red plant between Incheon International and Seoul, Korea

I've been wondering for years about what this plant might be, but I've never found anything about it. I found a picture of it here, but it's not a closeup picture. It grows all over in the sandy marshes between Incheon International Airport and Seoul. Any help in identifying it is appreciated. ···日本穣^? · 投稿 · Talk to Nihonjoe 02:37, 26 December 2009 (UTC)

That's a beautiful picture! Can you discribe the plant a little, height, flower type, etc.? Gandydancer (talk) 04:17, 26 December 2009 (UTC)

I wish I could as that would make it easier to identify. As it is, I've only seen it as close as you can see in the picture, and I've wondered about it for almost nine years now. ···日本穣^? · 投稿 · Talk to Nihonjoe 04:55, 26 December 2009 (UTC)

It sounds like this is something very dear to your heart and I hope you can find the name. Are you from Korea? I'm pretty familiar with most of the plants in the US and the only one here that I know to grow in such profusion in sand at ocean's edge is "ice plant", but it is a succulent and you mentioned marshland. It is here: http://en.wikipedia.org/wiki/Aizoaceae Gandydancer (talk) 05:39, 26 December 2009 (UTC)

Not really dear to my heart, just piqued curiosity. When I can't figure something out, it just bugs me. No, I'm not from Korea, though I am interested in many things about Korea. As for it being marshland, I was just guessing that's what it was since it's right by the coast. Does that plant turn red at any time of the year? ···日本穣^? · 投稿 · Talk to Nihonjoe 05:55, 26 December 2009 (UTC)

I've never been to Korea and from the picture it is hard to tell if that is sand dunes or marsh land. If it is sand dunes, a succulent would be a good guess. Yes, in bloom it would look like the picture. Gandydancer (talk) 06:07, 26 December 2009 (UTC)

It could be salicornia. Here's a photo of the salt marshes near where I live that shows the reddish color of salicornia in the winter [19].--Eriastrum (talk) 23:31, 26 December 2009 (UTC)

I think you nailed it! Just curious, where do you live? Gandydancer (talk) 04:30, 27 December 2009 (UTC)

At a guess in or near Morro Bay, California? Nil Einne (talk) 10:10, 27 December 2009 (UTC)

The only problem being that these plants are red in summer (late July, early August). ···日本穣^? · 投稿 · Talk to Nihonjoe 19:24, 27 December 2009 (UTC)

I do indeed live near Morro Bay on the central coast of California. The salicornia does start to turn reddish in the late summer and fall; it is reddish throughout the cooler months.--Eriastrum (talk) 20:48, 27 December 2009 (UTC)

What causes our windup toy to spark, and what are sparks?

My grandson got a windup toy for Christmas today. You wind it up and that makes a bar rotate over a flat, round circular surface. Two small spokes hang down from the bar and rapidly circle the flat plate producing sparks. We are guessing that the two spokes are flints and that the circle, which looks like sandpaper, is a steel sandpaper. Then we got into a discussion about what was needed to produce...sparks? (we weren't sure exactly what we were trying to "prove"...). At any rate, we came up with oxygen, heat (from friction), and a 3rd thing, and I'll be darned if I can remember what it was. Any thoughts on this process would be most welcome. We did wonder if there is a little heat in the sparks, and we guess that there is, since I know that they can be used to start tinder.

The discussion went on to "exactly what is a spark?", and is this process similar to the (I think) electron transfer that causes the little shocks that one occasionally experiences in a dry atmosphere when rubbing two things together. Is there "heat" in those shocks?

Sorry for the very poor explanation - my physics knowledge is very limited. Gandydancer (talk) 05:06, 26 December 2009 (UTC)

Oxygen, heat (source of ignition) and.....FUEL (something to 'burn', though oxidation may be technically more accurate), See also Fire. Your flint and 'sandpaper' hypothesis sounds very likely.
A spark (from a fire or flint) would be a tiny piece of fuel that is in fact burning (educated guess only!). In you second para ("little shocks"), you are referring to static electricity, not the same as the toy sparks. Though static is same as the 'sparks' from a 'trigger' type gaslighter. see Piezoelectricity. (both electricity, though produced by different processes)
Heat?, yes there would have to be though it occurs so quickly you can't feel it. Lightning is also static electricity can be extemely hot, though only for perhaps microseconds (thousandths of a second) --220.101.28.25 (talk) 05:37, 26 December 2009 (UTC)

More accurate definition of Spark "A spark is a small airborne ember or particle of red-hot matter." ie. doesn't have to be actually burning--220.101.28.25 (talk) 05:48, 26 December 2009 (UTC)

... consequently, oxygen is not needed for sparks to form. However, sparks in an oxygen environment can result in flame. Nimur (talk) 13:01, 26 December 2009 (UTC)

Yes, so it appears, though usually oxygen would be present. Most sparks seen would be coming from a fire, though in this case (original question) they are produced from friction, similar to a grinder. Be interesting to see a grinder used in a nil oxygen(vacuum?) environment See also Ember, which may put a slightly different slant on it. --220.101.28.25 (talk) 14:00, 26 December 2009 (UTC)

Some delicate machining work takes place in a nitrogen- or argon-flooded work area, to minimize chance of flame. The metal flakes kicked out during machining do still glow (from blackbody radiation, which does not require flame). Systems which will eventually store pure (~100%) oxygen or other strong oxidizers are specially checked for metal burrs, flakes, or any other tiny metal particles, because the ability to spark just by shaking around these tiny flakes (e.g. steel-on-steel collisions or friction resulting in sparks) may result in fire, if the atmosphere is very highly oxidizing. The fuel source can be the steel particle itself, which can burn in the presence of oxygen. This cleaning procedure, along with other cleaning to remove any flammable fluids or hydrocarbon lubricants, is part of what rates a system as "oxygen clean" - i.e., reduces the risk of spark ignition and flame, when oxygen is added. The OP's discussion of "a 3rd thing" is in reference to the Fire triangle. Sparks are the ignition, not the result, of fire. Only in unusual cases (such as those I mentioned) can the sparking material itself also be the fuel for the fire. Again, keep in mind that the only things necessary for fire are fuel, oxidizer, and ignition - normally, we take the oxidizer for granted, because we are in Earth's atmosphere. But flame can still exist, for example, in underwater welding or in the vacuum of space, if we bring the oxidizer with us. Hypergolic fuels provide chemical self-ignition, and combust without any spark to ignite them. Nimur (talk) 14:37, 26 December 2009 (UTC)

Sparks can certainly be the result of fire. I once burned an aluminium lamp socket, by accidentally shorting it. It made a fountain of very very bright white sparks about 6 feet high. A spark is burning metal, so it's fuel and ignition at the same time. (A spark can also be electrical.) Ariel. (talk) 00:40, 27 December 2009 (UTC)

I am reading everything and thank you! I have looked at the links provided and looked at spark plugs and flintlocks as well. I have begun to rule some things out, however I am still far from an explanation. Certainly one problem is my problem with a poor understanding of physics. As time permits I will try to come to an understanding of where I am at. Again, thanks. Gandydancer (talk) 18:15, 26 December 2009 (UTC)

There are two kinds of sparks. One is electrical, like a static shock, or a spark plug. The other is burning metal. Electrical sparks are blue (in normal air anyway), and metal burning is various colors, including blue, but usually red or white.

Contrary to assumptions, when you rub metal in a grinder, it is not the heat of friction that causes the sparks, but rather tiny pieces of metal that break off, and burn in air. Most metals are flammable. Aluminium is extremely flammable, and iron too - they are just pretty hard to ignite. You can see iron burn, by using fine steel wool - you can light it with a match. And aluminium is burned in the space shuttle. Both simply need a lot of air to burn, and by making tiny pieces you have a large amount of air relative to the surface area of the metal, and it burns.

The reason iron does not normally ignite, is that when the surface rusts (aka burns) it releases some heat, but the heat is absorbed in the mass of the metal, and it never gets hot enough to get going. Aluminium protects itself with a surface layer of alumina, that is very hard, and seals the metal from any additional air. Ariel. (talk) 00:36, 27 December 2009 (UTC)

I have nothing to add to Ariel's excellent answer but my name compels me to contribute to this thread, so I will confine myself to complaining that we seem to be lacking an article here. Spark is a disambiguation page and has no article listed that really covers this meaning, ember really refers to wood or coal fires. There is, however, spark testing which has a section that explains about metal burning (see spark testing#Compressed air method). SpinningSpark 01:37, 27 December 2009 (UTC)

Arie, you say "Contrary to assumptions, when you rub metal in a grinder, it is not the heat of friction that causes the sparks, but rather tiny pieces of metal that break off, and burn in air." So in our toy, the flints move over the metalic surface flicking off tiny chips of metal (the fuel), and in the presence of ozygen they will burn (oxidize). And the friction is needed to heat the metal to its burning point? Say, thanks for that spark test page! I'll check out the toy tomorrow and see if we can ID the metal. I think the kids will enjoy that, and of course I will as well. Gandydancer (talk) 04:00, 27 December 2009 (UTC)

Coughing while asleep?

Last time that I was ill, I had a cough that could be heard through the (admittedly, rather thin) wall and door for my bedroom. Others in the house reported that I sometimes coughed in the middle of the night, even on nights during which I had no memory of waking up. Is it possible to cough while asleep, or is it more likely that I was awake for such a short time that I didn't remember it in the morning? Nyttend (talk) 05:50, 26 December 2009 (UTC)

I don't see why not. Sleep covers a wide range of neurological states, some much deeper than others. People certainly move while asleep (tossing and turning, for example), so I don't see why in some of the lighter stages of sleep you would not also cough if your airway was irritated. --Jayron32 06:29, 26 December 2009 (UTC)

Both sound equally likely to me. You can do a lot that you don't remember during brief waking periods at night. Vimescarrot (talk) 11:49, 26 December 2009 (UTC)

Also, this could explain you being more tired in the morning due to lack of REM sleep if you're only sleeping lightly all night due to the coughing. ···日本穣^? · 投稿 · Talk to Nihonjoe 16:49, 26 December 2009 (UTC)

what is the evolutionary advantage of appreciating natural beauty?

It is almost instinctive to like a vista, grand views, rushing rivers, the smell of flowers, green leaves... well maybe it's advantageous to prefer forests over deserts, but even humans find deserts beautiful sometimes. Ignoring the issue of appreciating the beauty of the opposite sex, why would an appreciation for beauty evolve at all? John Riemann Soong (talk) 06:06, 26 December 2009 (UTC)

Our article Aesthetics is related and will be of interest, though it is a philosophy article and not an evolutionary biology article. Comet Tuttle (talk) 06:43, 26 December 2009 (UTC)

I have a hypothesis that it's due to the brain getting new patterns, because obviously beauty can go stale. --Ayacop (talk) 07:49, 26 December 2009 (UTC)

I am a person that does a fair bit of natural beauty hunting and I'm not sure that appreciation for natural beauty is an evolved trait at all. One could easily argue that it is the result of environment rather than hereditary. If it is evolved then it might not have been caused by direct evolutionary pressure but as a by product of something else. Noodle snacks (talk) 08:35, 26 December 2009 (UTC)

But what would the trait piggyback on? John Riemann Soong (talk) 09:14, 26 December 2009 (UTC)

I don't think that hard science can explain it. It seems to me that one must go into the realm of Noetic Science http://en.wikipedia.org/wiki/Noetic_sciences for an explanation, but most people are not willing to go there. Gandydancer (talk) 18:08, 26 December 2009 (UTC)

The visual beauty you refer to utilizes the sense of sight in a special way. The satisfaction one experiences may be not so much linked to the external stimuli but to the sensation of the functioning of one's visual apparatus. Sight is highly developed in humans in various ways. Expansive vistas of nature illuminated by sunlight allow for a full exploitation of our visual capabilities. This situation might be compared to having a car that can go 400 mph and finally finding a place to utilize that ability. I don't know why there would be pleasure associated with viewing these vistas. But it may be a pleasure just relative to settings that use a far narrower range of our abilities. I doubt if people who live amidst a breathtaking setting are constantly appreciating their view, at least not in a way that they are keenly aware of. Bus stop (talk) 00:04, 27 December 2009 (UTC)

The question carries an implicit assumption that perception of beauty is a function that gives a survival advantage, like having an opposable thumb. IMHO perception of beauty is a survival confirmation only.Cuddlyable3 (talk) 00:13, 27 December 2009 (UTC)

Some things we find beautiful are beneficial things - fertile rolling green hillsides, for example, are likely to contain lots of good food and shelter. I'm not sure how relevant that actually is, though, since it doesn't universally apply. Barren wildernesses are often considered beautiful, and I would think they were best avoided. --Tango (talk) 00:24, 27 December 2009 (UTC)

I believe I have heard someone, I think in National Geographic Magazine, of about a year ago, describe deserts as the most beautiful of places. Bus stop (talk) 00:28, 27 December 2009 (UTC)

Why does wanking feel good? I'm pretty sure our consciousness combined with some formerly advantageous traits can have spurious results. —Preceding unsigned comment added by 92.17.229.48 (talk) 00:52, 27 December 2009 (UTC)

Even fish can have fetishes (sticklebacks I think). 67.243.1.21 (talk) 03:26, 27 December 2009 (UTC)

Also, on the same topic, if one is indoors for a day or two or three, and then one emerges into a not at all spectacular environment — it may look beautiful. If it were merely an urban or suburban setting of no noteworthy natural vistas, but merely say, a sunny morning, after a rain — the glistening objects, however banal, could be of breathtaking beauty. This once again shows that the appreciation of natural beauty is a relative thing. Compared to being in a dimly lit indoor space for three days, any kind of outdoor space in sunshine would be aesthetically pleasing. This also illustrates that we get used to the breathtaking aesthetics of nature, and fail to see it. But I think it has to do with the full utilization of our senses. In a dimly lit room the eyes have limited opportunity to do all that they are capable of doing. This is just conjecture, or original research. Bus stop (talk) 19:01, 27 December 2009 (UTC)

does MSG change taste with pH?

Other than the change in taste caused by vinegar, etc. Does glutamate that is +1 or at the pI taste differently than glutamate at -1? Would -2 glutamate (e.g. I add baking soda to MSG) smell like fish? John Riemann Soong (talk) 09:18, 26 December 2009 (UTC)

Help someone? I really can't find it in the literature, and otherwise I think I'll end up experimenting to find out. (Though I don't think I can add enough baking soda to get to deprotonate the amino group....) John Riemann Soong (talk) 07:08, 27 December 2009 (UTC)

Problem with Japanese appliances in European plugs

Hi, I'm trying to charge my Japanese Nintendo DSi (for the plane ride home of course!) in Ireland, and I'm having trouble. I have the proper prong converter and a voltage converter that works for Canadian appliances, and every other Japanese piece of electronics that I've brought with me (though admittedly I don't have anything as heavy duty as the DS), but the DS is non-responsive. At most I get a single flicker of the charging light when I plug it in, but it won't be charged at all after an hour plugged in. The DS works (for a couple of seconds before the battery goes flat) so I'm convinced nothing's been burned out, and I charged it fine just 3 days ago (in Japan), so I'm lost as to why I wouldn't be able to charge it here. Does anybody know of any reason why I might be having this problem? Thanks! 83.71.33.178 (talk) 09:31, 26 December 2009 (UTC)

It's not really possible to diagnose your problem without having the equipment in front of me to test but here are some possibilities. First off, without checking with a meter, you cannot be sure that your converter is providing the right voltage. Many charger circuits nowadays are "universal"; that is, they will accept a wide range of input voltages. They will consequently still charge even if you have not provided the voltage you think you have. If your DS is not "universal" the difference is explained. A more likely explanation is that there is a fault with the connection cable between voltage converter and DS (do you use the same cable for any other piece of equipment?). The brief flicker of the charging light would seem to indicate a fault, either with the cable, or worse from your point of view, with the circuitry in the DS. That kind of brief flicker is often indicative of something that has gone open circuit, you still get a brief burst of current through capacitive coupling when first connected. SpinningSpark 10:48, 26 December 2009 (UTC)

Yeah, the brief flicker was suspicious to me too, so I checked with the exact same combination of voltage converter/prongs on some other electronics and it worked fine, so I figure it must be something on the DS, or the AC adapter for the DS that was aborting the connection or just failing for some reason. The DS is still definitely in working order though. The DS and the AC adapter are not universal (no built in converter), the AC adapter says it's for 100V/110V, which should work fine with the Canadian voltage converter, usually built for ranges around 120V, though it might be designed to be more sensitive so as to protect the electronics, I don't know. 83.71.33.178 (talk) 11:25, 26 December 2009 (UTC)

Usually, small/cheap converters only convert the voltage and not the frequency - and some devices care about that which is a common cause for problems. Ireland is 220v/50Hz - but Japan is a mess with some places being 110v/50Hz and others 110v/60Hz - which usually means that Japanese-made equipment is tolerant of frequency differences. But it's really hard to know how to solve your problem without more information.

My best advice is to buy an in-car charger for the DS (they are pretty cheap) and charge it up from the 12v outlet on a car. Of course this assumes you have access to a car. The good thing about this approach is that (a) it's definitely going to work - all cars everywhere work at 12volts and (b) you'll be able to use the car charger when you get back to Japan, so the money you spend isn't wasted on a gadget you'll never use again. If you don't have access to a car - you might look to see if there is a USB charger for the DS that would let you charge it from a computer...I guess you have access to a computer because you are reading this reply on one! SteveBaker (talk) 14:17, 26 December 2009 (UTC)

Statements that begin "All cars everywhere..." are usually exaggerations. Austin 10 1932-1933, Wolseley Eight 1946-1948, Volvo PV444/544 1947-1961, Renault Dauphine 1956-1968, DAF 33 1969-1971, and Citroen 2CV 1948-1990 are all cars that are running somewhere on 6-volt batteries. Cuddlyable3 (talk) 21:04, 26 December 2009 (UTC)

This is true - and remember there are still quite a few positive-earth cars on the road, albeit of a similar vintage to those mentioned. A somewhat greater risk these days is finding that the car you want to use as a power source doesn't have a cigar lighter... Tevildo (talk) 21:28, 26 December 2009 (UTC)

Oh good grief. Firstly, it you're going to be pedantic - at least get it right: the 2CV switched over to 12volt batteries in 1966 (I have restored a '68 2CV and I know this for a fact). So perhaps I should have said "all cars less than ~38 years old"...except that the virtual impossibility of buying things like headlamp bulbs and car radios for 6v systems means that a very large proportion of positive ground and 6volt cars that are still on the road after 40 years have been retro-fitted with negative-earth and 12volt batteries. Only the most fanatical car restorer would try to keep such antiques on the road with their original electrical systems. Now ask yourself whether ANY of those 40 year old 6v cars have cigarette lighters with modern connectors - and whether the negative-earth ones are wired such that just about anything you'd plug into it would blow up? (The couple of car nuts who I know who have their Mini's still wired up with negative earth evidently wired up their after-market accessory sockets the 'conventional' way because I know they use them to charge their walkie-talkie's). The answer I gave is very nearly 100% perfect. This kind of pedantry on the RD is getting really tiresome guys. Sheesh! SteveBaker (talk) 04:02, 28 December 2009 (UTC)

Or you could go buy a USB charger and do it that way, as you've obviously got access to a computer! 61.189.63.130 (talk) 00:40, 27 December 2009 (UTC)

(I already said that). SteveBaker (talk) 04:02, 28 December 2009 (UTC)

December 27

Male involvement in pornography

1) How do females who work in the realm of pornography maintain a non-platonic relationship with a male counterpart while being involved in pornography?

2) How do males get involved in pornography-related careers? Are there aesthetic criteria they must meet, or does any guy get in? Both points seem odd to me when I think about it. DRosenbach ^{(Talk | Contribs)} 03:09, 27 December 2009 (UTC)

By "non-platonic" does that mean the opposite of Platonic love, as this linked-to article would define it? Bus stop (talk) 03:20, 27 December 2009 (UTC)

Well, I figure that there might be a pornographic actress who is married and tries to become pregnant with her husband and work might 'get in the way.' DRosenbach ^{(Talk | Contribs)} 05:24, 27 December 2009 (UTC)

Oh, I see. I misunderstood. I was thinking the non-platonic relationship being referred to was with the male porn star. You should have referred to the male as a "significant other" or some such locution. Or I should have thought about it more. Bus stop (talk) 05:45, 27 December 2009 (UTC)

I think the solution is two-fold: 1. People in porn tend to be young, and 2. Most males or females might be willing to forgo their normal sense of jealousy for the bragging rights (and supposed sexual benefits) of dating a porn star. It's also presumably possible that the type of personality that would pursue a career in the porn industry is one that would tend toward a single lifestyle. And, for what it's worth, a fair portion of porn doesn't actually involve significant penetrative sex. ~ Amory (u • t • c) 13:28, 27 December 2009 (UTC)

I've seen two documentaries on the pornography business in general. Any woman can get in. Just like any acting, it is mostly just luck to become a star. As for men, both documentaries stated the same thing. Men begin in gay movies and, if they are star quality, they move into hetero movies. Many don't make the jump because the pay drops severely for men when they move from gay to hereto movies. The exceptions are very rare. For example, some lady wrote into her contract that she would only do anal sex with her husband. So, he got to be in her movies - but unpaid. Both documentaries also pointed out that the modern (post-VHS) pornography business is very different from the 50s through the 70s when the business was still run like a movie business. Now, it is a distribution business. The product is not important, just the quantity and availability. -- kainaw™ 03:34, 27 December 2009 (UTC)

Are you saying that all men who are in porn were in gay porn first? Dismas|^(talk) 06:12, 27 December 2009 (UTC)

yeah, that seems like an implausible reality. DRosenbach ^{(Talk | Contribs)} 13:57, 27 December 2009 (UTC)

I agree, very implausible. --Tango (talk) 14:49, 27 December 2009 (UTC)

Apparently some people need to read up on what "exceptions" means. I personally haven't tracked the filmography of every male porn actor. I am only relaying the content of two documentaries. -- kainaw™ 16:18, 27 December 2009 (UTC)

Nowadays, with internet distribution, naught but self-censorship prevents anybody from filming themselves doing whatever they want and attempting to sell it. The difference between art, blogging, and pornography is a very thinly legislated line that serves mostly for marketing purposes; there is no shortage of upscale user generated content/amateur pornography which is marketed as art of varying grades; etc. Probably the best answer to this question can be found in the humorous set of FAQs on Wikipedia's own Talk:Penis:

“ Q3: I would like to upload a picture of my penis.

A3: Unfortunately, the realities of supply and demand are not in your favor. There is a large supply of Wikipedia editors willing to photograph their penis in the name of science. However, the demand is much lower. If you feel that your penis is more deserving of placement on the article page, you are free to make your case below.

”

The same is probably true of male pornography - the reality of supply and demand does not favor males entering the industry. One way to change that equation is to act in alternative pornography, where there is (presumably) less supply. But nothing requires any member of the pornography community to ever act in anything they do not consent to (this is a well-defined legal distinction between a consented and non-consented act, e.g. exploitation or human trafficking). As such, the only barrier to males' porn success is marketability - the reality is, there is less demand for them. Nimur (talk) 17:24, 27 December 2009 (UTC)

I know what "exceptions" means - you said they were very rare. That may be true, but it sounds implausible to me. --Tango (talk) 17:46, 27 December 2009 (UTC)

The answer to both questions has changed slightly over the last few years as "home-based" porn has turned out to be rather profitable. Our articles on Heather Harmon and Wifey's World indicate that the answer to 1) is "with no trouble at all" and the answer to 2) is "have a hot wife". Your mileage may vary an enormous amount, of course. The old story about males having to go through gay porn first is probably not as entrenched as it used to be; the easiest way to become a male porno actor these days appears to be by simply buying a decent digital video camera, hiring the girl for POV work, and working out some kind of distribution deal either through an existing network or by starting up your own website/mail order. Matt Deres (talk) 19:37, 27 December 2009 (UTC)

LOL, By the way, if there's a science to pornography, I may have to go for my MSc! Do they still comp you for home study? Matt Deres (talk) 01:01, 28 December 2009 (UTC)

Big bang?

Certainly there is substantial evidence of cosmic expansion, but what is the evidence restricting this expansion to only empty space? I mean, to say something is not expanding is like saying that it's not a part of the universe. The Earth is expanding underneath us while we all and everything around us expand as well. Considering its size though, the earth expands quickly in relation to us, so gravity, right? It seems they're trying to make this expansion be relative to some fixed point, but that leads back to a big bang which mathematically has been shown not to work. --Neptunerover (talk) 03:55, 27 December 2009 (UTC)

Um..what? Sorry, it's just not clear to me what you're saying. The Earth is not expanding appreciably, and any minute changes that occur in its volume are not related to the metric expansion of space. The expansion of space can truly be thought of simply as solid objects getting farther apart. And where has the big bang been shown mathematically not to work? I think that would be news to a lot of physics enthusiasts at this desk. Someguy1221 (talk) 04:07, 27 December 2009 (UTC)

Sorry, I think I mixed two questions there, really, I hadn't meant to bring gravity into it initially when I started the question. Isn't the big bang in conflict with quantum mechanics because of how it tries to jam a whole universe into a little plank space? I thought I read something about that anyway. I'm just wondering what the proof is that things are staying the same size relative to the space between them expanding. --Neptunerover (talk) 04:29, 27 December 2009 (UTC)

(EC) Gravity is NOT caused by earth's expansion. The earth is NOT expanding. Who is that 'they' you are talking about? The Big bang expansion is not relative to a fixed point. And the Big bang has NOT been shown not to work. Dauto (talk) 04:10, 27 December 2009 (UTC)

I guess I mean the scientists who study the expansion of the universe. And by the way, how could gravity from expansion be disproved? Constant acceleration. Its the same thing whether the earth is pushing us or pulling us.--Neptunerover (talk) 04:35, 27 December 2009 (UTC)

Disproved? Occam's razor isn't a proof, but there are lots of bizarre explanations that would account for ordinary phenomena in bizarre-seeming ways. I'm not sure we disprove them, so much as go with models that make more sense to us... -GTBacchus^(talk) 04:38, 27 December 2009 (UTC)

Exactly, make as few assumptions as possible. Constant size is an assumption, though a very understandable one to make. Einstein taught us though about relative perspectives being equal. Is the Earth pushing, or is it pulling. You say tomato...--Neptunerover (talk) 04:49, 27 December 2009 (UTC)

Except that the earth expanding model doesn't work. Try explaining how come the surface of the earth does not hit the moon within your expanding earth thingamagick model. Dauto (talk) 05:57, 27 December 2009 (UTC)

That's just a reverse of the same model, though instead of using size as a fixed reference point, it switches over to space.--Neptunerover (talk) 06:07, 27 December 2009 (UTC)

I understand what you are saying. But the problem is that this alternate model DOESN'T WORK. If the earth were expanding at such a rate it would hit the moon in short order. Dauto (talk) 06:13, 27 December 2009 (UTC)

I mean the Big Bang uses size as a fixed reference point while planets bulging into each other is just a switch of reference points. The goal should be to avoid those.--Neptunerover (talk) 06:14, 27 December 2009 (UTC)

Meaning please... Dauto (talk) 06:17, 27 December 2009 (UTC)

Okay, the big bang model keeps everything the same size, with only the distance between celestial objects changing. The opposite model would keep the spaces between everything constant while the objects increase in size, filling the space between them until there is no more empty space. Neither of those models works, so the space between objects expands while the objects expand as well. With everything expanding at the same time, it's not something that can be measured except against how it was in the past. It can only be indirectly verified, with redshift and I think, gravity. --Neptunerover (talk) 06:44, 27 December 2009 (UTC)

Why does space expanding not work? The space between gravitationally bound objects doesn't expand, is that where the confusion is coming from? --Tango (talk) 00:16, 28 December 2009 (UTC)

Neptunerover, if assuming that everything is expanding affords a better explanation of the phenomena than assuming that everything is staying the same size, then I'd say you've got something. Until then.... I don't see any gain in switching to that extremely counterintuitive model. Can you come up with some experiment that would distinguish everything-growing from not-everything-growing? If not, then it's not a testable hypothesis, and it's not in the realm of science at all. -GTBacchus^(talk) 06:58, 27 December 2009 (UTC)

See, that's why I asked the question. I noticed in a few articles where the assertion is made that the expansion is not in the size of things, but only in the space between them, but there's no citation for that, so I'm just a David Hume here saying, how do they know? If expansion is limited to only certain parts of the universe, then, why? I think it makes more sense the other way, and I think it sort of solves some things too. Like how can the universe be so young with all we know about the age progression of stars.--Neptunerover (talk) 07:29, 27 December 2009 (UTC)

Is there a constant for the gravitational force that could be compared to the rate of the accelerating universal expansion? That could be sort of like a test, I think.--Neptunerover (talk) 08:28, 27 December 2009 (UTC)

With that though, something may need to be accounted for with the Doppler effect, since with this idea of a uniform expansion, the distance between objects will not increase as much as it would if they were to stay small while just separating in space.--Neptunerover (talk) 08:54, 27 December 2009 (UTC)

With another way of looking at gravity (not a better way, but just another way(assuming it fits all the evidence)), maybe that could help people in figuring out a way of repelling it. Hey, and if nobody could copyright that, wouldn't it be great? --Neptunerover (talk) 10:06, 27 December 2009 (UTC)

Ok, wait a second. Neptune, just so I'm completely clear on what you're saying... Based on this section of your talk page, you are suggesting that the sensation of gravity may be interpreted not as us being pulled toward the Earth, but rather as the Earth pushing up against us as it expands? Is that right? Someguy1221 (talk) 10:20, 27 December 2009 (UTC)

I think so. When we consider we're dealing with spacetime, then maybe thinking of cosmic expansion as being an expansion through time as opposed to an expansion through space (which would be like an explosion) could help overcome this counterintuitive concept of an incessant bulging of everything. But what would expansion through time be? Another tricky hurdle of thought is required for that. --Neptunerover (talk) 11:24, 27 December 2009 (UTC)

Looking around us, even though everything is bulging, we don't see things bulging, because of what everything is bulging in relation to, which is nothing. Looking at it this way, the Earth stays the same size because there is nothing for it to be getting bigger than (Like the big bang has everything start from nothing, but if everything is getting bigger than nothing, does that require any actual change in size? With nothing to compare size to, I'm not sure there would be a noticeable size difference in things that are expanding in relation to nothing.) So the Earth gets bigger in relation to nothing, meaning its size stays the same. But if the earth is now staying the same size, what about gravity? It's the interchangeability of space and time that lets us keep the earth the same size in space while it remains expanding forward in time, and gravity is then the response to that expansion. That's what I'm thinking anyway.--Neptunerover (talk) 11:55, 27 December 2009 (UTC)

How does something "expand in time"? And why are space and time interchangeable? I'm no scientist, but I've hung around this refdesk for a while and I've never heard of either of these concepts. Vimescarrot (talk) 13:25, 27 December 2009 (UTC)

I just meant moving forward in time while considering what could possibly be a cause of that. --Neptunerover (talk) 20:06, 27 December 2009 (UTC)

I was thinking of spacetime as needing to remain steady, meaning if one thing occurs in space, then it needs to be accounted for in time as well, and vice versa. --Neptunerover (talk) 22:13, 27 December 2009 (UTC)

There is just one problem with this model: IT DOESN'T WORK! To create a sensation of gravity through expansion the earth's surface would have to be expanding at a rate of 9.8 m/s². Other planets with different surface gravity would have to be expanding at different rates to match their surface gravities. That does not fit your uniformly expanding universe. Your model is also unable to explain gravity's inverse square law. This model is no-good. Dauto (talk) 14:13, 27 December 2009 (UTC)

Okay. I thought it seemed too easy. --Neptunerover (talk) 14:55, 27 December 2009 (UTC)

I think you are confused about how the equivalence principle applies. It does not at all imply that the Earth is expanding—it implies that our sensation of gravity is completely physically equivalent to constant acceleration. Those are not the same thing, at all. --Mr.98 (talk) 15:36, 27 December 2009 (UTC)

So it doesn't imply the Earth is expanding, but rather accelerating in all directions at once. I get it. --Neptunerover (talk) 20:42, 27 December 2009 (UTC)

And that fits right along with the universe accelerating in all directions, so I think you're right. --Neptunerover (talk) 21:05, 27 December 2009 (UTC)

Maybe they should call it cosmic acceleration in all directions instead of expansion or inflation, which gives the impression of an explosion outward.--Neptunerover (talk) 22:19, 27 December 2009 (UTC)

OK, I'm now convinced that you are just playing around. --Mr.98 (talk) 00:07, 28 December 2009 (UTC)

I am sincerely not trying to play with or fool around with anyone. I'm just playing with an idea, and if it's right, then there is no proof for this non-uniform cosmic expansion model they're trying to push. I'm not saying it therefore must be wrong. How would I know? I certainly don't know all the details. It just seems to me they're assuming something without there being a valid basis for doing so, and so I came here wondering if there is any actual proof. I don't think they can prove that some things are expanding in relation to nothing while other things are staying the same size in relation to nothing. The word 'nothing' by itself does not indicate a size. You cannot say (the)nothing is small or that it is big, since these terms only apply to actual things that can be measured. (the)Nothing is absent of anything measurable, and so measuring anything in comparison to it is folly. Even trying to explain it could be folly because sentences don't only mean one thing. I just think for the big bang to suggest that universal expansion is an expansion in the size of the universe in comparison to nothing is absurd.--Neptunerover (talk) 04:12, 28 December 2009 (UTC)

The expansion of space is not "in comparison to nothing". The benchmark is the speed of light. See Metric expansion of space. Gandalf61 (talk) 07:21, 28 December 2009 (UTC)

Hey yeah, it mentions right there in [1.1] about expansion into time, which I was asked about before. So I thereby cannot be accused of making things up.--Neptunerover (talk) 07:53, 28 December 2009 (UTC)

Okay, let me look up this speed of light thing. --Neptunerover (talk) 07:53, 28 December 2009 (UTC)

Sorry, but I'm lost on what you mean by the benchmark of lightspeed. That sounds like another frame of reference, but doesn't the speed of light always recede as you approach it, like a rainbow? --Neptunerover (talk) 08:21, 28 December 2009 (UTC)

Not like a rainbow (which is a fixed angle, though perception of distance varies with terrain), but asymptotically (i.e. we can get as close as we like to it, but never reach it in finite time). Dbfirs 09:04, 28 December 2009 (UTC)

thanks for the term. --Neptunerover (talk) 11:03, 28 December 2009 (UTC)

Maybe the problem is that there are two ways of approaching the speed of light. One is through time, and the other is through space. Through space would be measured by size and mass, while through time would be what, energy? --Neptunerover (talk) 08:45, 28 December 2009 (UTC)

Don't you need both space and time to measure any speed?
Like you, I have never been happy with red-shift explained by receding galaxies or by expansion of inter-galaxial space. I have always felt (intuitively) that we are missing a wider viewpoint that would explain observations, but I don't think expansion (or contraction) of the local metric provides any alternative explanation. Meanwhile, metric expansion of 3-D space (excluding gravity-bound clusters such as galaxies) into the dimension of time seems to fit the observations, so it seems to be the best model at present. Dbfirs 09:13, 28 December 2009 (UTC)

I'm not sure time is well enough understood to say something like that. There's that problem with not being able to get a reading on both a particle's location in space and velocity. Maybe that is because its velocity is through time, whatever that might mean...?Neptunerover (talk) 11:03, 28 December 2009 (UTC)

IT rather surprises me that anybody ready to embrace an expanding earth would be worried about an expanding universe being absurd. Rest assured though. There is no reason to worry. The universe expansion is a fairly simple thing. It's nothing more than the idea that the galaxies are moving away from each other. That movement has been clearly observed through the doppler effect. Most galaxies' light is observed to have a redshift which means they are moving away from us. Dauto (talk) 13:43, 28 December 2009 (UTC)

... or that the doppler effect is caused by some other aspect of space-time that we don't understand?
Does metric expansion of inter-galactic space imply that far-distant galaxies are actually travelling away in the sense of a real velocity? Dbfirs 14:48, 28 December 2009 (UTC)

Yes. By definition if their distance from us is increasing over time than they are travelling away. But extra care must be taken whenever talking about the speed of a distant object such as a distant galaxy. Unlike local movement It is NOT impossible for a distant galaxy to move away from us faster than the speed of light. Dauto (talk) 16:06, 28 December 2009 (UTC)

Point taken. I have this intuitive distinction between "relative velocity" meaning increasing distance with time, and "travelling" meaning "covering distance over time". I agree that, since there is no preferred inertial reference frame, the distinction is only in my imagination. Dbfirs 23:31, 28 December 2009 (UTC)

Small text is by Ref. Desk convention used for frivolous interjections. It should not be used for interpolative debating on the subject, neither by the OP, nor by someone who doesn't sign their post, and especially not by someone who lives in the error that IT'S is a posessive pronoun, as in the nonsensical construction "it's velocity is". Cuddlyable3 (talk) 00:52, 29 December 2009 (UTC)

I apologize, I've never experienced small text, and I was unsure how to respond to the small text that was in front of a paragraph of regular sized text, while making it clear the response was to the small text, so I thought responding with small text might work. I should've signed both sections I added with the one edit, and that was my mistake. (I'll copy the signature now to show when it was added.) --Neptunerover (talk) 01:21, 29 December 2009 (UTC)

diamond vs ceramics

Is diamond a ceramic? give reasons. —Preceding unsigned comment added by Kumar 3069 (talk • contribs) 07:06, 27 December 2009 (UTC)

That certainly sounds like a homework question, apologies if that assessment is wrong. There's plenty of information in both the ceramic and diamond articles that should allow you to reach a conclusion. If there's something you don't understand, then come back and ask a specific question. Mikenorton (talk) 12:12, 27 December 2009 (UTC)

Interesting question. Unfortunately, I don't know the answer. The Wikipedia page on ceramic has this description:

“ A ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (e.g., a glass). Because most common ceramics are crystalline, the definition of ceramic is often restricted to inorganic crystalline materials, as opposed to the non-crystalline glasses. ”

It seems that the answer to the question hinges on the definition of ceramic. Diamond meets the criteria of being inorganic, non-metallic, solid, and crystalline. The part that's not so clear is whether it is "prepared by the action of heat and subsequent cooling." Heat is involved in at least some methods of synthesizing diamond, but whether that counts as "prepared by the action of heat and subsequent cooling" I don't know.

Can someone versed in material science provide a technical definition of what ceramic is? --71.185.178.230 (talk) 17:53, 27 December 2009 (UTC)

It may also depend on your definition of "organic". One sometimes sees chemists who will expand the title of "organic" to all carbon-based compounds even when they aren't associated with living things. Dragons flight (talk) 16:15, 28 December 2009 (UTC)

Our article on solids says that ceramics are polycrystals (i.e. contain "grains"), which diamonds would not. Our articles seem not to concur as to whether this is part of the definition or just something that's typical. If someone does indeed know the answer to this question, the articles I've linked to (and ceramic) need to be harmonized. Matt Deres (talk) 04:47, 28 December 2009 (UTC)

nanocrystalline materials

What are the applications of nanocrystalline materials in automobiles? —Preceding unsigned comment added by 117.204.22.16 (talk) 07:12, 27 December 2009 (UTC)

Modern electronics rely heavily on semiconductors, which can be described as nano-crystalline materials. Nearly every modern automobile will contain at least a few semiconductor parts for control, power regulation, sensors, and any onboard computers. Nimur (talk) 17:39, 27 December 2009 (UTC)

Semiconductor devices usually are monocrystalline, not nanocrystalline. -Yyy (talk) 09:48, 28 December 2009 (UTC)

Naked Singularities, Hawking Radiation, and Quantum Gravitation

Well, today I for no reason suddenly started to think about Black hole electrons. Well, but as the mass of a blackhole decreases, its Hawking Radiation should rise and electrons therefore are not stable. But then I knew if the electron was a blackhole, it would have to be a Naked Singularity. I then looked on the article for Hawking Radiation. Well, the sentence "Hawking radiation is required by the Unruh effect and the equivalence principle applied to black hole horizons" under "Emission Process" immediately caught my eye. So is it that Naked Singularities do not radiate Hawing radiation? Or (assuming electrons are black holes) they don't emit radiation just for some other reason like because the energy is more than the total energy of an electron(obviously including the mass energy from $E=mc^{2}$)?The Successor of Physics 14:31, 27 December 2009 (UTC)

That analysis relies on semiclassical theory, and only makes sense for black holes with masses much larger than the Planck mass. Otherwise the notion of Hawking radiation is not applicable - you need quantum gravity. 69.140.13.88 (talk) 16:33, 28 December 2009 (UTC)Nightvid

Tomato

Are tomatoes vegetables, or fruits? Or both? cheers--79.38.22.37 (talk) 15:37, 27 December 2009 (UTC)

See tomato and let us know if you have further questions. -- kainaw™ 16:20, 27 December 2009 (UTC)

Indeed. The article has an entire section that answers this. Ultimately, this is a question better suited for the language desk, because it deals with contextual word usage and the ambiguity of vernacular English. Both fruit and vegetable (...and tomato!) are terms that mean different things in different contexts. Typically, only "fruit" has a well-defined scientific meaning; in such a context, the tomato is clearly defined as a fruit. Nimur (talk) 17:33, 27 December 2009 (UTC)

According to Wiktionary, a Vegetable is:

1. Any plant.
2. A plant raised for some edible part of it, such as the leaves, roots, fruit or flowers, but excluding any plant considered to be a fruit, grain, or spice in the culinary sense.
3. The edible part of such a plant.

So a Tomato is a vegetable under (2) - but in a culinary sense, it's not considered to be a vegetable if it's also a fruit/grain/spice.

The Wiktionary definition of a fruit is:

1. (botany) The seed-bearing part of a plant, often edible, colourful/colorful and fragrant, produced from a floral ovary after fertilization.
2. Any sweet, edible part of a plant that resembles seed-bearing fruit, even if it does not develop from a floral ovary; also used in a technically imprecise sense for some sweet or sweetish vegetables, such as rhubarb, that resemble a true fruit or are used in cookery as if they were a fruit.

The Tomato is the seed-bearing part of the plant - it's edible, colorful and fragrant and it comes from the floral ovary - so there is utterly no doubt that it's a fruit under any sense of the term.

But under the definition (2) of "vegetable", it's ALSO a vegetable...unless you are talking in a culinary sense - in which case it's only a fruit.

However, people misuse the words "fruit" and "vegetable" all the time. Scientifically - they are definitely fruit AND also vegetables. In culinary usage - they are technically only fruit - but they are rarely called that because they aren't sweet like most other fruit. In common parlance they are almost always called vegetables. In government regulations, they are all over the map. It's a mess. But from a scientific perspective - they are most certainly fruit. SteveBaker (talk) 17:39, 27 December 2009 (UTC)

Actually, you have one bit backwards. A tomato is only a culinary vegetable, and not a culinary fruit, because it is used in savory applications. From a culinary (cooking) perspective, a fruit is something used in sweet applications, while a vegetable is used in savory applications. This is different from the botanical definition of fruits, a tomato is a botanical fruit because it is the seed bearing part of the plant. All culinary fruits are also botanical fruits, but there are MANY botanical fruits that are culinary vegetables. See also cucumber, squash, eggplant, chili pepper, etc. etc. which are, like tomatos, also botanical fruits, but not culinary fruits. In the botanical world, the word vegetable has no meaning, since vegetable is used only in the culinary world. A plant scientist would use words like "stem" or "leaves" or "fruit" to describe plant parts... --Jayron32 21:16, 27 December 2009 (UTC)

Not if you trust Wiktionary. It's saying that while scientifically, all fruits are also vegetables - in culinary terms, something is either a fruit or a vegetable...never both. But the dictionary definition of a fruit is unambiguous for things that are scientifically fruits - and only difficult in culinary terms when things like Rhubarb is considered to be a fruit. I don't see any way (with the Wiktionary definitions) for anyone to legitimately claim that a Tomato is NOT a fruit...although only non-culinary applications of the term 'vegetable' apply to the Tomato. I can't find another way to interpret that...unless of course Wiktionary is wrong. SteveBaker (talk) 03:11, 28 December 2009 (UTC)

What??? Steve, I can't really follow your logic here. Using the definitions you report (I won't check Wiktionary now because it might have changed in the mean time), a tomato is not a fruit under definition (2), because it's not sweet. So that means it does satisfy definition (2) of vegetable, because the exclusion "unless considered to be a fruit...in the culinary sense" does not apply (again, because it's not sweet).

Am I missing something in your argument? As far as I can see it's pretty simple: "Not sweet" implies "not a culinary fruit". (Except, I guess, for fruits that are so sour that it's difficult to taste their sweetness, but that are usually used with added sugar — I'm thinking of e.g. lemons here.) --Trovatore (talk) 07:36, 28 December 2009 (UTC)

"From a culinary perspective, a fruit is something used in sweet applications" ... "All culinary fruits are also botanical fruits" is arguable, I'd say. Rhubarb would likely be considered a fruit by most cooks (as "something used in sweet applications") but it's definitely not a botanical fruit. Carrots, however, quite firmly classed by cooks as a vegetable, are delicious in a "sweet application" such as carrot cake or Christmas pudding. The distinction isn't important (unless you're a government official trying to create red tape). Tonywalton ^Talk 01:36, 28 December 2009 (UTC)

Well, there aren't bright lines here; there are some foods that will stradle some of these distinctions; however those are very few. --Jayron32 01:52, 28 December 2009 (UTC)

Nonlinearity of the sRGB and Adobe RGB color spaces

The Wikipedia articles on sRGB and Adobe RGB articles state that both color spaces are nonlinear (with the latter having a gamma of 2.2 and the former approximately 2.2). So does it mean that if you use an image editor to create composite of a 50%-opaque image superimposed on another, 100%-opaque image, you are not getting the same resulting image as you would if you project the two source images onto the same reflective screen at half intensity? It seems to me that such non-linearity would create all sorts of unexpected weirdness when one is using an image editor, but I never noticed any. What gives? Do image editors internally use representations that are linear w.r.t. intensity when applying transformations and remap the pixels to the nonlinear color spaces on saving? Or is it true that the working representations are actually nonlinear, just that any "unexpected weirdness" is not noticed by most people? --71.185.178.230 (talk) 18:29, 27 December 2009 (UTC)

Bear in mind that the gamma in the image file is intended to counteract the 'typical' non-linearity present in the display device - such that when you double the brightness going into the image - you get twice the amount of light coming out again. Hence, you certainly wouldn't expect the results of adding two non-linear things together. Since gamma(a)+gamma(b) is not equal to gamma(a+b) - you would not expect your experiment to work unless the image editor is handling it right. In an ideal world, the loader for the sRGB image would convert it into a linear image for editing and convert back into non-linear as it displays it and when it writes it out to disk again...however, that's not always done properly - and a lot depends on which image editor you're using. But slightly more concerning is that you're talking about compositing by transparency...and that gets complicated since it depends on whether the alpha channel is also gamma-corrected. The whole thing is a bit of a mess...complicated by the fact that it's rare for any real-world display to have a gamma of 2.2 and not something wildly different. SteveBaker (talk) 02:59, 28 December 2009 (UTC)

Sound pressure, sound intensity, sound loudness, and decay with distance

This webpage http://www.sengpielaudio.com/calculator-ak-ohm.htm says that: "The sound pressure level (SPL) decreases with doubling of distance by (−)6 dB..... The sound pressure decreases with the ratio 1/r to the distance.

The sound intensity level decreases with doubling of distance also by (−)6 dB...... The sound intensity decreases with the ratio 1/(r^2) to the distance.

The loudness level decreases with doubling of distance also by (−)6 dB..... The loudness decreases with the ratio 1/(2^0.6)r = 1/1.516r to the distance."

My questions: a) how is the result "loudness decreases with the ratio 1/(2^0.6)r = 1/1.516r to the distance" obtained and is it correct? b) Is "loudness level" as described on that webpage the same as how subjectively loud a sound-noise is measured in db? c) What would sound intensity be in layperson's terms if it is not subjective loudness? d) Elsewhere on the page a "cylindrical wave" is mentioned. What would that be? Thanks. 92.24.73.139 (talk) 19:21, 27 December 2009 (UTC)

See Loudness and Stevens' power law for some of the ways in which people have tried to quantify psychological responses to stimuli. The equation you have a question about above is basically Stevens' power law for hearing. Stevens based his law by taking average results across a large number of people; basically its a law based on repeated experimental trials. It works a lot like the Scoville scale does for chili pepper hotness; its based on interviewing many many many people on their perception based on quantifiable initial conditions. For hearing, what you do is you place someone in an environment with a certain dB at a certain distance from the source, and then you ask them to rank their perception of the loudness of the sound. --Jayron32 21:10, 27 December 2009 (UTC)

The page means by "cylindrical wave" a wavefront that is spreading on a cylidrical surface. A wave emanating from a point in all directions will spread on a spherical wavefront. This is not usually particularly useful for sound systems as it wastes power sending some of up into the sky and into the ground. To generate a cylindrical wavefront the generator needs to be a line rather than a point. A column loudspeaker unit with drivers facing in all (horizontal) directions will approximate to this, see line array. A cylindrical wavefront spreads out in two dimensions only rather than three. SpinningSpark 22:16, 27 December 2009 (UTC)

Your power law for loudness doesn't look right. wouldn't it be 1/r^0.6 ? Dauto (talk) 01:30, 28 December 2009 (UTC)

I don't know, that's why I'm asking. 89.242.213.201 (talk) 10:41, 28 December 2009 (UTC)

The website's formula is wrong. Dauto (talk) 14:34, 28 December 2009 (UTC)

No it's not wrong, they are just not very clear in what they are saying. The basic relationship here is that subjective loudness is roughly reckoned (at most frequencies and levels) to double with an increase of 10dB sound level. This is an inexact relationship as it involves messy human beings. For a given decibel increase the loudness increases by x 2^dB/10. For a doubling of distance the sound level change is -6dB and consequently the loudness change is 2 ^{- 0.6}. SpinningSpark 22:56, 28 December 2009 (UTC)

PTSD and hippocampus

In the page on PTSD, it says that Vietnam soldiers with PTSD were shown to have hippocampuses 20% smaller than avg. I had part of my hippocampus taken out and have been diagnosed with PTSD and mentioned that point to my neurologist and he said that such claims were purely anecdotal. Should that part be edited? —Preceding unsigned comment added by BroncoBuff (talk • contribs) 20:00, 27 December 2009 (UTC)

Discussion of a specific page should go on the respective Talk page, in this case Talk:Post-traumatic stress disorder. If the claim regarding the hippocampus is poorly-sourced, then editing may be necessary. If it has reliable sources, then one should support alternative viewpoints supported by similarly-reliable sources (conversation with a neurologist not being one of those). -- Scray (talk) 20:22, 27 December 2009 (UTC)

An interview with a neurologist would be a reliable source if it were published in a third-party, reputable journal or news outlet. If you conducted the interview yourself (presumably in the process of dealing with your own situation), then it constitutes original research and can't be cited in the article. There should be no shortage of research into physiological manifestations of PTSD - Hypotheses and controversies related to effects of stress on the hippocampus: An argument for stress-induced damage to the hippocampus in patients with posttraumatic stress disorder. (Journal of Hippocampus, 2001, vol. 11), seems to be a a good review of the different viewpoints about this particular physiological effect. Jeez, there's a journal for everything!Nimur (talk) 20:40, 27 December 2009 (UTC)

Let me note that our hippocampus article has some information on this. The basic story is that there is extensive evidence that many types of long-term stress, including PTSD, are associated with reduced hippocampal size -- we even have a pretty decent understanding of the biological mechanism by which stress damages the hippocampus. There is, however, no evidence that I am aware of that damage to the hippocampus can cause PTSD. Looie496 (talk) 15:47, 28 December 2009 (UTC)

Finite element method - solid or shell?

When using a linear FE code such as NASTRAN or a non-linear code such as LS-DYNA, when should you use solid elements instead of shells?

I.e. If the shells thickness is 5mm could a shell element of 1mm x 1mm be used? If not why not and what happens to any theoretical assumptions used? —Preceding unsigned comment added by Cjread58 (talk • contribs) 20:32, 27 December 2009 (UTC)

Solid element FEA is much more computationally intense than shell based methods. In return, it usually better matches the real-world physics. However, depending on your actual problem and parameters, this extra accuracy may be unneeded. It may also lead to instabilities. As far as element size, you might want to read the CFL condition for numerical stability. Also note that in addition to numerical stability, your element size also determines your smallest resolvable feature (or highest resolvable spatial frequency, if you prefer to think in that domain). See sampling or resolution (we appear to be lacking an article about the generic mathematical/sampling meaning for "resolution", but most other uses (e.g. optical resolution) follows the same conceptual rules as the generic-case numerical system. Nimur (talk) 21:06, 27 December 2009 (UTC)

Lost question

I wrote question a few days ago. it seems to have got lost or erased. Why is a gyroscope stable when spinning, but not when still? —Preceding unsigned comment added by 79.75.24.71 (talk) 23:32, 27 December 2009 (UTC)

I would tell you to look at the gyroscope page, except that the explanation there, while it might be technically correct, is pretty useless. If you understand the explanation - you don't need it. If you need an explanation, the one there will not help you. I would suggest using other resources besides wikipedia. Ariel. (talk) 00:59, 28 December 2009 (UTC)

Hey, Ariel — how about giving a try to improving that article? Comet Tuttle (talk) 01:08, 28 December 2009 (UTC)

angular momentum conservation. Dauto (talk) 01:21, 28 December 2009 (UTC)

Here's my attempt at a non-mathematical explanation. You can compare a fast-spinning gyroscope to a fast moving object, such as a bullet in space (no gravity). A small amount of momentum change in the bullet perpendicular to the bullet's direction of travel is not going to alter significantly the direction of travel. It is for a similar reason that a small amount of angular momentum change (proportional to torque × duration of torque application) is not going to change significantly the orientation of the gyroscope. It is important to know that this is true only when the angular momentum change is small relative to the angular momentum the spinning rotor has. The system of gimbals in a gyroscope allows the spinning rotor to be in any orientation relative to the enclosing environment to which the gyroscope may be mounted. In other words, the gimbals prevent transfer of torque to the spinning rotor. When the rotor is not spinning, even small angular momentum change can alter its orientation significantly. This is because, compared with zero (or something very close to it), even quantities otherwise considered quite small is quite large. --71.185.178.230 (talk) 17:24, 28 December 2009 (UTC)

An even simpler response would be to compare almost any object in motion, such as a spinning top or a running human, with that same object at rest. The chief concept is that, in motion, balance can be often be found even in a position that, if maintained during rest, would not exhibit balance. Thus, a top at rest cannot be balanced on its point and a human with many of the freeze-frame positions of running would not be balanced if the runner would be at rest. DRosenbach ^{(Talk | Contribs)} 19:22, 28 December 2009 (UTC)

While that appeals to a familiar observation, I don't think that's much of an explanation. --71.185.178.230 (talk) 20:27, 28 December 2009 (UTC)

71.185.178.230 - did you learn your explanation somewhere, or did you make it up? Because it doesn't sound right to me. And DRosenbach, 71.185.178.230 is right - that's not much of an explanation. A spinning top is stable because it is a gyroscope, not because it's moving. And human running is not stable at all, the human is constantly inputting energy to keep upright. Ariel. (talk) 21:39, 28 December 2009 (UTC)

I came up with the explanation myself. Which part of the explanation do you have a problem with? --71.185.178.230 (talk) 21:47, 28 December 2009 (UTC)

The whole thing. Force causes an affect relative to mass. It makes no difference how much momentum is already in the device. In your bullet explanation: The bullet is moving left, and you are pushing it down. The motion down will only care about how much force it was given in the down direction. It does not care at all about the motion to the left. If you measure how far down it travels after a certain time, that amount will be identical, no matter how fast it's going to the left. Ariel. (talk) 21:57, 28 December 2009 (UTC)

What you missed is that, in the bullet example, although the change in vertical motion (and velocity in particular) is not affected by the horizontal velocity, the amount of deflection (measured as an angle) is. The situation with a gyroscope is wholy analogous: the spinning rotor carries a certain amount of angular momentum, which determines its axis of rotation. If the angular momentum is large, small angular impulses (from sources such as air movement, friction at the gimbal joints etc) are not going to affect the angular momentum of the spinning rotor enough to affect the axis of rotation by much. Think of it this way: the angular momentum of the spinning rotor is a (long) vector in 3D space; the small external angular impulse is another (short) vector in 3D space. The vector sum of the two (and the direction it points at) is dominated by the long vector. --71.185.178.230 (talk) 22:21, 28 December 2009 (UTC)

I don't understand gyroscopes very well, but my best explanation of them is this: Imagine an upright gyroscope. (i.e. a wheel parallel to the ground, eg a sideways bicycle). Press down on one side of the gyroscope, and it will start to move down, causing the whole thing to tilt sideways. But one moment later, the part of the gyroscope that was moving down, is now on the other side of the gyroscope. It's still moving down. But now it's causing the whole thing to tilt in exactly the opposite direction. Ariel. (talk) 21:50, 28 December 2009 (UTC)

December 28

most appropriate article

I know the Wikipedia is not a "how-to" manual but many articles contain examples nonetheless to demonstrate or illustrate how something is done to help eliminate confusion in the article just as an image is added to an article to improve the article's clarity by incorporating the visual senses. In this regard I have a spreadsheet which uses an Excel add-in Solver function that incorporates linear programming to select the most cost effective combination of ingredients for production of several products to find the amounts of various foods to produce a completely balanced meal within the desired number of calories. The spreadsheet allows various foods to be added or subtracted (zeroed) from the spreadsheet in order to create a meal consisting of the specified amount of calories, fat, carbs, protein and fiber or any other constraint the user desires to use. There are several possible articles in which this example might fit best such as the article on Excel or its SOLVER add-in. It might also fit best in the simplex article or some dietary article. My question is what article readers will benefit from it the most?

(Note: There may be a better wiki converter routine than the one used to produce the wiki listing below so I have included a link to the .xls beneath it.)

Meal Planner	Source of nutrient	'	'	'	'	'	'	'	'	'	333.33	Objective calories	'	'
Variables	potatoes	milk	chicken	flax	c veg	egg w	soy	rice	raisins		RHS		LHS	Slack/Surplus
Objective Function	80	80	60	60	40	50	90	160	130	=	Target Calories		291.61
fats	0	0	9	45	0	0	36	13.5	0	=	66.67		66.67	0.00
carbs	0	48	4	16	32	0	20	140	124	=	200.00		200.00	0.00
protein	0	32	44	12	8	48	32	16	4	=>	50.00		50.00	0.00
Fiber	0	0	0	8	4	0	6	4	4	=>	16.67		16.67	0.00
	Results: Servings and grams
Servings	0	0	0	1.14379085	0.753449528	0.25493222	0	1.125635439	0
Grams	0	0	0	13.7254902	7.534495279	3.059186638	0	45.58823529	0
												L1 - To change the number of calories per day or the number of meals per day.
	grams											B26-B29:J26-J29 - To zero out conversion factor for grams to calories per nutrient type
	0	0	1	5	0	0	4	1.5	0			B20-B23:J20-J23 - to enter number of grams per nutrient for each food.
	20	12	1	4	8	0	5	35	31			N3 - Attained calories
	1	8	11	3	2	12	8	4	1			B10-11:J10-J11 - Results in number of package servings and grams
	1	0	0	4	2	0	3	2	2			Note: Spreadsheet utilizes the SOLVER add-in.
	calories per gram
	0	9	9	9	9	9	9	9	9
	0	4	4	4	4	4	4	4	4
	0	4	4	4	4	4	4	4	4
	0	2	2	2	2	2	2	2	2

The Excel worksheet may be downloaded from personal diet example. 71.100.6.153 (talk) 01:37, 28 December 2009 (UTC)

For what it's worth, and I have not the faintest idea what it's doing, what it's for, or whether the numbers it shows actually make sense, it loads and appears to produce some sort of results in my completely non-Microsoft environment (NeoOffice 3.0.1 on Mac OS X). So if it's meant to illustrate something specific to Excel or SOLVER these may not be appropriate articles to link to it. Maybe you could simplify it and generalise it to illustrate something about linear programming? Tonywalton ^Talk 02:00, 28 December 2009 (UTC)

Actually there are many good examples of this very process all over the net especially at many university sites that want to get students up and running quickly in the use of Excel and its Solver add-in. I had been using a computer program written in Visual Basic v6 to do the same thing but the Excel layout here is actually simpler and more adaptable to other uses. The idea here is the application of linear programming specifically to finding meals based on set number of calories and meals per day that produce a balanced diet according to any particular dietary regimen choice rather than intending to serve as a general application of linear programming. Some food or dietary article then me thinks best. 71.100.6.153 (talk) 02:30, 28 December 2009 (UTC)

IMHO, this is not the kind of thing Wikipedia needs - as you know - this is not a "HOW TO" guide. However, since you evidently don't agree with that assessment, I think you should go to one or more of those pages and start discussing it on the 'Talk:' page there. If there is widespread support for this amongst the authors of those articles - then you can go ahead and do it - if not, then it's better to quietly give it up because of the "not being a how-to guide" thing. You could (I suppose) "Be Bold" and just add it and see what happens - but since my personal inclination is contrary to that, I'd just go in there and revert your change - so you'd end up having to discuss it anyway. SteveBaker (talk) 02:46, 28 December 2009 (UTC)

A better converter would certainly help make it more presentable but what about just the link to the actual spreadsheet. In what article might that best find an acceptable place? 71.100.6.153 (talk) 02:52, 28 December 2009 (UTC)

Is this a project which would be better suited to the mandate of one of our sister projects — perhaps Wikiversity? TenOfAllTrades(talk) 03:23, 28 December 2009 (UTC)

Presenting the whole concept of linear programming is definitely worth the facility offered by the Wikiversity since for one thing the entire economy of the former Soviet Union used it to replace supply and demand but what I would hope to accomplish here is to provide individual readers interested in a mathematical means of creating a balanced diet that meets whatever calorie need they might choose both an example and a place to start, which might then lead them later to a full blown Wikiversity course. 71.100.6.153 (talk) 06:06, 28 December 2009 (UTC)

strange astronomical sight

Today at around 8:30 pm, while on a walk, I saw something pretty strange. The full moon was shining brightly through... a perfect circle of white clouds. The circle seemed so perfect that I think it needs a specific scientific explanation. I took two pictures with my cellphone. This happened in La Mesa, CA, USA. I'm really curious what could cause such a phenomenon. Supersonic jet, meteorite? Probably something more than just a trick of the wind. Thank you in advance. —Preceding unsigned comment added by 68.8.170.157 (talk) 05:04, 28 December 2009 (UTC)

I think semitransparent clouds covered whole sky more or less evenly, and the light from round moon highlighted a portion of these clouds. Hence the round cloud. (Igny (talk) 05:10, 28 December 2009(UTC))

Are you sure it was composed of clouds? Ice crystals in the upper atmosphere can produce such an effect, see 22° halo and Circumhorizontal arc 218.25.32.210 (talk) 05:21, 28 December 2009 (UTC)

The moon isn't going to be full for a couple of days, so your judgment of what makes for a "perfect circle" is a little suspect. Could you upload the pictures somewhere for us to check out? Without seeing the pictures, I'd tend to concur with my colleagues above - upper atmosphere droplets or crystals can be thin enough to be nearly invisible unless strongly lit from behind by the moon. Matt Deres (talk) 06:19, 28 December 2009 (UTC)

Here is the current moon in Maine, though perhaps it may be different in Caflifornia since you are farther west. :=) http://www.calculatorcat.com/moon_phases/phasenow.php?tcv=31 Gandydancer (talk) 07:15, 28 December 2009 (UTC)

I posted a picture of the moon with a 22^ohalo. did the phenomenon you saw look anything like that? Dauto (talk) 14:15, 28 December 2009 (UTC)

If someone wouldn't mind fixing the currently incomprehensible initial sentence in the 46° halo article -- I would do it myself, but I haven't a clue what it's trying to assert, and I left a message on the talk page which doesn't look like it's been visited about 60 times in the last year by no one who edited except for a page assessment. DRosenbach ^{(Talk | Contribs)}

I took a stab at cleaning up the language. It looked like some serious grammar issues, but I think I was able to make heads and tails of it. --Jayron32 20:58, 28 December 2009 (UTC)

I've tried for about an hour and a half to place the pictures online but had no success. Can someone walk me through the process? My cell is t-mobile. —Preceding unsigned comment added by 68.8.175.233 (talk) 22:10, 28 December 2009 (UTC)

IPs are not permitted to upload images directly to Wikipedia. You will have to upload it to Commons, or else to some other site like Flickr and then link it. SpinningSpark 23:17, 28 December 2009 (UTC)

Fischer esterification with amino acids -- worried about the protonated amino group

Is there anything particularly tricky about esterifying an amino acid with an alcohol with acid? The amino group is protonated and I'm worried that'll discourage protonation of the carboxyl group. But .... is the protonated amino group such a big problem? I know the alpha-COO- group is particularly acidic and would definitely not like a second proton, but since the amino group is electron-withdrawing right -- that should encourage esterification even if the carboxyl group is particularly hard to protonate? John Riemann Soong (talk) 05:31, 28 December 2009 (UTC)

Extraterrestrial intelligence

The universe is so large and there may be many undiscovered galaxies, which means possible undiscovered stars and planets. There may be undiscovered planets in habitable zone. Then why scientists deny the possibility of existence of extraterrestrial intelligent life forms? --Qoklp (talk) 10:50, 28 December 2009 (UTC)

Do they? Vimescarrot (talk) 11:48, 28 December 2009 (UTC)

Take a look at the SETI article, there are an awful lot of scientists involved in actively looking for extraterrestial intelligence. SpinningSpark 11:54, 28 December 2009 (UTC)

I was going to say something along the same lines. A good scientist probably would not "deny the possibility of existence of extraterrestrial intelligent life forms?". There may be a lack of verifiable evidence from reliable sources. People claim to have been taken on board 'spaceships' by 'aliens' but not too many of these people are 'rocket scientist' types (I may be being a bit uncharitable here). Space is certainly very big, lots of galaxies, star systems, planets etc. It would be a "waste of space" wouldn't it? I recall that Carl Sagan believed that it was very possible. --220.101.28.25 (talk) 12:03, 28 December 2009 (UTC)

See also Rare Earth hypothesis and Drake Equation --220.101.28.25 (talk) 12:14, 28 December 2009 (UTC)

No scientists really think that there wouldn't be extraterrestrial intelligent life forms, somewhere, at some time. They just deny that there is any evidence that humans have yet been in contact with any E.T.s., or have differing opinions on the odds of humans ever having contact with said E.T.s. (See the Drake Equation for one attempt to narrow down the parameters of what it would require to be able to communicate with an E.T. civilization.) --Mr.98 (talk) 16:49, 28 December 2009 (UTC)

It is a mystery how the OP can link to the article habitable zone that speaks about "the likeliest candidates to be habitable and thus capable of bearing extraterrestrial life similar to our own" but allege that scientists deny this possibility. Actually reading the article would be a good move. Cuddlyable3 (talk) 00:03, 29 December 2009 (UTC)

Anatomy classes - Truth or myth?

Anatomy class: The Professor sticks his finger right up the guts of a dead man, pulls out his finger and sticks it in his mouth. The students just stand there, paralyzed at what they see. He says: Now, go ahead and do the same thing, each of you. Freaked out, the students take several minutes but eventually take turns sticking their fingers up into the guts, and then sucking on them. Once everyone is finished, the Professor continues on with his lesson. He: now, the most important quality you must possess is a keen observation. You see, I stuck in my middle finger up the butt, and I sucked on my index finger. Now, learn to pay attention.--Quest09 (talk) 19:55, 28 December 2009 (UTC)

Neither - it's a joke. --Tango (talk) 19:58, 28 December 2009 (UTC)

OK, it sounds as a joke and it´s told as a joke. But how can you know that it didn´t happen at least once?--Quest09 (talk) 20:05, 28 December 2009 (UTC)

You could ask that about any joke told in the form of a story, couldn't you? Vimescarrot (talk) 20:09, 28 December 2009 (UTC)

There's a variation of this regarding testing urine for the sugary indication of diabetes, as well. (Which snopes has a page on, incidentally.) It's the kind of joke that professors like to tell. Har har. --Mr.98 (talk) 20:18, 28 December 2009 (UTC)

Well, diagnosing diabetes by tasting the urine (if it's sweet there is glucose in it and the patient is probably diabetic) is a genuine diagnostic technique. It isn't used these days since we have little sticks that change colour when exposed to glucose, so doctors prefer those. Urine is perfectly sterile and safe to drink, there is really no downside to the technique. --Tango (talk) 20:47, 28 December 2009 (UTC)

I myself have seen it with my own eyes. Intended as a joke, of course, and with urine (well, yellow liquid) rather than a corpse. Tevildo (talk) 20:25, 28 December 2009 (UTC)

An apocryphal story also told about a chemistry professor who "tastes" a beaker of urine by dipping one finger in it and sucking another finger. Professors like their jobs, which is why you can be pretty sure this never happened. - Nunh-huh 20:24, 28 December 2009 (UTC)

Yeah, my 9th grade bio teacher did this with urine, too. DRosenbach ^{(Talk | Contribs)} 20:33, 28 December 2009 (UTC)

This is an easy one. Assume it is true. A professor purposely tricks students into potential viral and/or bacterial infections. If not treated properly, they could be life threatening. The only result of this insanely stupid act is that it becomes a common joke. In what version of reality is such an event possible? Perhaps on the show House (which is a very strange version of reality where doctors only see one or two patients a week). -- kainaw™ 21:49, 28 December 2009 (UTC)

Since the term "guts" may refer to any part of the Human gastrointestinal tract it is not obvious that the OP means the cadaver's anus, nor how gustation of rectal debris might advance one's education in anatomy. To research further on the subject that interests the OP, see this article and the acronym ATM; tutorial videos produced by dedicated professionals are available but deprecated since they do not provide health warnings, and there are probably somebody's mothers and sisters there. Cuddlyable3 (talk) 22:58, 28 December 2009 (UTC)

This joke is also in Mark Perakh's collection of Russian jokes. [20] bibliomaniac15 23:05, 28 December 2009 (UTC)

If we inject oxytocin into a female

Human female or any cow - whatever is at hand- would she start producing milk? --Quest09 (talk) 20:03, 28 December 2009 (UTC)

As our lactation article explains, there is a lot more needed than oxytocin. Looie496 (talk) 23:16, 28 December 2009 (UTC)

New way to generate electricity - has this been proposed before?

I would like to know if this idea has been proposed an if there is a name for it. Otherwise, will this work? The idea is to use buoyancy of a large ammonia filled balloon to generate power, where the power ultimately is obtained from the vertical temperature gradient in earth's atmosphere:

Have a large ammonia (gas) filled balloon tethered to a reel that's connected to an electrical generator with a clutch. Right below the balloon is a small thermally insulated tank. To achieve the desired altitude of 10-20km it might be necessary to add an additional hydrogen filled balloon of adequate volume to the top. The clutch is only engaged when the balloon is rising. A small engine can reel the tether in when the clutch to the generator is disengaged.

When the balloon is released at ground level it will rise up and generate electricity. It will rise to an altitude of 10km or more where ambient temperature will cool the ammonia down to below its boiling point of about -33 degrees Celsius with some thermal delay. All liquid ammonia that forms runs into the insulated tank at the bottom. Once enough liquid has run into the tank the balloon will begin to descent while the tether is reeled in with little resistance. More ammonia will condensate until the balloon has dropped to an atmospheric level almost equal in temperature to the boiling point of ammonia, at which point the insulated tank is closed at the top. The balloon will continue to descent, but start to slow down again as the weight of the hanging tether is reduced.

When the balloon stops descending the clutch is engaged again and the insulated tank is opened again for the ammonia to evaporate, which will happen at the relatively warm ambient temperature at the low altitude. The process repeats. During design the size of the balloon(s) and the tank need to be balanced with the weight of the tether to ensure that the system rises very high and descends quite low, but not so low as to risk hitting the ground.

As a bonus, if the balloon is reeled in all the way, the liquid ammonia could be used to drive a heat engine like an ammonia "steam" engine to have the liquid replaced by warmer gaseous ammonia of equal mass for the next round. Multiple systems like this can work in parallel at different stages simultaneously.

The ammonia and possible hydrogen balloons need to be semi collapsible and can be constructed using technology such as a Hoberman Sphere covered in a stretchable membrane. I did the math and if this is possible then the cube-square law makes this method of electricity generation very effective and scalable.

196.210.200.164 (talk) 20:59, 28 December 2009 (UTC)EonZ

The two big challenges I see are that it requires a lot of moving parts to move very large volumes of gas, and also that the heat capacity of air (particularly stratospheric air, at rather low pressure) is quite limited; that means that we need to move large volumes of air into contact with our system, and that the chilling/warming cycles may take a long period of time. Both of those factors mean a lot of balloons and some costly equipment.

While I'm not familiar with such a generator operating in the manner you describe, there are a number of pilot projects which exploit temperature differences between surface and deep-ocean water. Our article on ocean thermal energy conversion gives the details. In those systems, they avoid the problem of collapsing and inflating balloons and reeling cables in and out by moving the ammonia working fluid up and down through fixed pipes. TenOfAllTrades(talk) 21:26, 28 December 2009 (UTC)

Yes, it would work. It's basically a Stirling engine with the hot and cold side separated by a great distance. Ariel. (talk) 21:30, 28 December 2009 (UTC)

Note that "it would work" is not the same as "would be a feasible way to generate electricity". There's lots of ways to technically generate electricity which, like this method, are not viable for commercial power generation. You can generate electricity by paying people to run on treadmills, or by capturing cow flatulence in large balloons and burning it, or by any number of wildass methods, the question becomes if these methods produce enough electricity at a low enough cost to be viable. I can't see where your method would... --Jayron32 21:42, 28 December 2009 (UTC)

At 10-20km the ammonia will be at reduced pressure so it needs a lower temperature to cause condensation than the boiling temperature at atmospheric pressure. Keeping the condensed ammonia liquid during the descent to warmer temperature could be done more reliably by locking it into a pressure vessel than in an unpressurized insulated tank. I am not sure how you prevent the balloon stabilising at an intermediate height. The weight of 10-20km tether is significant. Unless your "small engine" can pull in the tether faster than the balloon sinks, the tether and possibly the balloon will hit the ground.

The balloon is at the mercy of any wind. Both the tether and the "small engine" must be strong enough to overcome all wind forces.

The balloon and its tether are hazards to aircraft. Legalisation of a no-flight volume will be needed, in principle a 20km radius hemisphere centred on the tether reel.

Pure ammonia is corrosive. The implications of a balloon full of ammonia hitting the ground anywhere in a populated area, and at an unpredictable distance if the tether breaks in a storm, are disturbing.

The Hoberman sphere is a complex multi-jointed construction that seems to give a lot of failure points and no advantage except increased weight relative to a simple flexible gas bag. Cuddlyable3 (talk) 22:19, 28 December 2009 (UTC)

There are any number of ways of exploiting a temperature gradient to extract energy - so the only real questions here are whether this is the most efficient temperature gradient to exploit - and if so, whether this is the best way to exploit it. My feeling on the first question is "No" - because geothermal approaches and (as TenOfAllTrades says) deep ocean temperature gradients are much more accessible and stable. If you absolutely had to exploit an air temperature gradient - then I suppose this might work - but the practical problems are pretty severe. Remember - you can extract energy from pretty subtle temperature gradients with things like the Drinking bird toy - or, more practically, with a stirling engine. SteveBaker (talk) 00:31, 29 December 2009 (UTC)

Electronic locator

Hello. I'm thinking of taking my little nephew out to play in a small wood (without any streams or water) and it seems likely that he'd want to run off and play hiding games. Perfectly natural, and good fun, but I'd feel more comfortable if I could 'tag' him in some way to make him easy to find quickly if need be. I'm imagining something small that straps to the wrist, that would feedback to something small I kept. Perhaps like 'homing beacons' in old spy dramas, with a little screen that shows roughly where he is and how far away. Or maybe audio feedback like a metal detector. I'm sure such things must exist. Any suggestions?

I'd even welcome suggestions on how to make my own, although I'd need a link to a good walkthough if it involves circuitboards. 86.176.48.114 (talk) 01:11, 29 December 2009 (UTC)

Here is an external commercial link you might try. 71.100.6.153 (talk) 01:29, 29 December 2009 (UTC)