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February 8

Embryological Skeleto/muscular development

Hello. I've been looking to find out information on whether in a developing human embryo, does the skeleton/bones or the muscle develop first? My understanding is that both are produced simultaneously through differentiation of the mesoderm, but I have surprisingly been unable to find much on this. Any references (preferably online) that would shed light on this matter would be greatly appreciated. 114.77.39.141 (talk) 03:45, 8 February 2012 (UTC)

Hmmm. Both can emerge from somites, in limb bud development, or from branchial arches. Chondrogenesis involves the condensation of precartilage into cartilaginous structures. Muscle patterning involves a more dynamic process involving founder cells/muscle precursor cells. See [1] for a useful reference. Wnt (talk) 06:26, 8 February 2012 (UTC)

This reference [2] gives more about tendon development, the physical link between bone and muscle. It seems that bone, tendon, and muscle are independently specified during development from the somite stage onward; but there is cross-talk from bone to tendon and tendon to bone (at least, in the expansion of projections already present) and from muscle to tendon also. In a quick search of OMIM ("enthesis"; "tendon AND insertion") I didn't find any condition where muscles form independently of tendons (and thus perhaps bone), nor have I ever heard of it. Given Nature's fondness for cruel juvenile humor such as the imperforate anus I'm quite surprised really. The authors of the paper I cited remark on the absence of similar mutants in mice (at least for FGF-based mechanisms). But somites, bone, muscle, tendon - these are a large part of the overall vertebrate body plan, and so we should expect the situation to be complicated and well regulated. Wnt (talk) 14:18, 8 February 2012 (UTC)

OP here. Thanks for both responses; however I must admit I am lost by all the medical terminology. Especially with the second article, could someone direct me to where specifically it talks about the developmental stages of skeletons and muscle. 114.77.39.141 (talk) 11:09, 9 February 2012 (UTC)

That paper focuses on more on tendons, which to me seem a crucial conceptual and physical link; Figure 3 illustrates that at mouse E12.5 the differentiating bone and muscle are separated by a band of tendon progenitors which are still relatively unorganized until E13.5. Note: The "E" notation for mice is less sophisticated than it looks - it just means the number of days since a vaginal plug (evidence of mating) is observed, with the first day called "0.5" because it is assumed they mated sometime during the night. Sometime around day 19-20 birth occurs, but baby mice are even less developed than baby humans (mouse eyes open at 13 days after birth vs. humans in the 6-month fetus; I think epithelial stratification [an equivalent of amphibian metamorphosis] occurs around 3 months in humans vs. E11.5 or so in mice). Wnt (talk) 08:19, 10 February 2012 (UTC)

Brownian motion as perpetual motion

Could Brownian motion be actually considered the perpetual motion in a closed system?--46.204.55.76 (talk) 05:37, 8 February 2012 (UTC)

If you do, you might as well include planetary orbits, too. StuRat (talk) 05:41, 8 February 2012 (UTC)

When it comes to energy, there ain't no such thing as a free lunch. See Maxwell's demon and Brownian ratchet. Red Act (talk) 05:46, 8 February 2012 (UTC)

To make things a bit simpler: Perpetual motion is not an impossibility; there's lots of things in the universe which are essentially in perpetual motion; the molecules in the air around you are in perpetual motion. However you cannot use such motion to do work; any attempt to use a system in perpetual motion to do work will result in the system "winding down", and losing energy until it reaches some state of equilibrium and becomes unable to do more work. --Jayron32 05:50, 8 February 2012 (UTC)

Except that's not really true. The molecules in the air, or things illustrating Brownian motion in general, still have continual energy inputs, e.g., energy inputs from the sun continually add energy to the molecules in the air in the atmosphere. It's not a closed system operating indefinitely, which is required for perpetual motion. --jjron (talk) 11:53, 8 February 2012 (UTC)

My understanding of it, building on Jjron's comment: Real-life (as opposed to ideally-modeled) Brownian motion is usually something like the motion of very small particles of say, dust, as have molecules of gas (e.g. air) collide with them. The molecules are only colliding because they are themselves moving — they have kinetic energy in the form of heat. Every time they collide with the dust particle, they lose a little energy. If they were thermodynamically isolated from any additional temperature source, they would eventually expend all of their energy on colliding and it would stop moving. So it's not really perpetual — it runs down, like everything does, if there isn't a source of input energy (e.g. if it is in a closed system). In practice such systems probably never wind down to that stage, I speculate, because the amount of energy needed isn't much, and once you approach temperatures like absolute zero, all sorts of other weird things start to occur... --Mr.98 (talk) 12:51, 8 February 2012 (UTC)

To be clear, a closed system is one which can exchange energy but not mass with its surroundings; this is in contrast to an isolated system, which can exchange neither energy nor mass. A thermodynamically closed system will exchange energy with its surroundings as long as the system and its surroundings are at different temperatures; if you have a sealed container with a hot beverage in it, heat (energy) will be conducted through the walls of the container until the container (and the coffee inside) reach the same temperature as their surroundings. A thermodynamically isolated system, on the other hand, can't exchange energy with its surroundings. All the parts of the isolated system will reach equilibrium with themselves, but the total amount of energy present and the effective temperature of that system will remain constant. In practice, it's impossible to achieve complete thermodynamic isolation, as energy can even be conveyed across hard vacuum by electromagnetic radiation.

The closed system will 'wind down' only until it reaches equilibrium with its environment. (Note that this works both ways—a cold can of soda will also absorb energy from its surroundings until equilibrium is reached.) The isolated system, on the other hand, would – in principle – remain at a constant temperature forever.

Mr. 98's statement about Brownian motion running down is mistaken. While a gas molecule that collides with a dust particle may itself lose some kinetic energy, that energy is transferred to the dust mote, which in turn can transfer energy to another gas molecule in the future. In an isolated system, the total energy (and temperature) of the gas-dust mixture will remain constant forever. (In a merely closed system, the gas-dust mixture will exchange energy with its surroundings until they're both at the same temperature, and then the system will stay at that temperature.) If you wait long enough, you'll find that the highest concentration of dust will be near the bottom of the box and very few dust particles will be near the top, but the dust will never settle completely; there will gradually be an equilibrium established between Brownian mixing and gravitationally-driven settling. (This is a form of sedimentation equilibrium.) TenOfAllTrades(talk) 13:50, 8 February 2012 (UTC)

I was assuming that the energy would not be exchanged with 100% efficiency and some of it will be converted into a non-useful form, ergo the running down. Is this wrong? --Mr.98 (talk) 14:23, 8 February 2012 (UTC)

Gas collisions are generally elastic collisions. What form would collisions due to heat energy be converted to? Heat? 216.197.66.61 (talk) 15:41, 8 February 2012 (UTC)

I'd considered that, but wasn't sure. Good to be corrected! (Though the fourth paragraph of the elastic collision article does put somewhat of a limit on that if we are talking about molecules, no?) --Mr.98 (talk) 17:11, 8 February 2012 (UTC)

Once you get into situations that are more complex than monatomic gases, then you have to account for energy finding its way into other modes—that is, into things like rotational and vibrational excitation of the molecules. The energy is always conserved, though, and the equipartition theorem even means that at equilibrium each mode stores essentially the same amount of energy. TenOfAllTrades(talk) 19:05, 8 February 2012 (UTC)

Sun leaving main sequence between 1 and 5 billion years from now

How much bigger suppose the sun to get between 1 and 5 billion years from now. Our article said 10% luminosity in 1.1 Gyr, 3.5 Gyr is 40%. What is 10%, 20% mean by growing luminosity. Does sun get 10 times larger in size, every billion years, 20 times larger in size every billion years. Is sun's RGB 250xs current radius 5000 times more luminosity it means 5000 times brighter, or 2000 times brighter. If 5000 times brighter means habitable zone surface temperature everywhere in our solar system is too hot,even 100 AUs away. 2000 times brighter is habitable zone at Saturn system, Neptune system, or Pluto system? I am all messed up confused right now.--69.229.39.25 (talk) 06:06, 8 February 2012 (UTC)

I notice that neither this nor your previous query further up the page have yet been answered. To be honest, I started to yesterday, but then gave up because I found both queries too confusing. Each seems to have several intertwined questions, which makes the task of answering more daunting. Also, both are written in English sufficiently imperfect as to be difficult to understand. You might want to think a bit about exactly what you want to know, and then write one or more simpler questions, clearly separated. In the meantime, Section 5 'Life cycle' within our article Sun includes a graph which you might find helpful, though the concept of effective temperature is not wholly straightforward.

To address what I can: the Sun's radius will only increase to about 110% of its current value in 1 billion years from now, and to about 130% of today's value in 5 billion years from now. I'm sure that you can work out how much that will increase its surface area, which is the main cause of its gradually increasing luminosity during the main sequence part of its lifetime, during which its surface temperature will remain roughly the same. Such modest changes in size are of course trivial compared to the distance of the planets from the Sun – for example, the Earth orbits the Sun at a distance of about 214 times (21400% of) the Sun's current radius.

When the Sun, now with a little less mass after 5 billion more years of fusion, leaves the main sequence and becomes a Red giant, it will indeed grow to a size comparable to the size of the Earth's orbit (and will for this reason will become more luminous), but its surface temperature will also drop (lessening the increase in luminosity a little bit). Since the changes in mass and so on associated with these processes will, as you have already learned, cause changes to the orbits of the planets, it's difficult to calculate exactly where everything will end up, and I'm not familiar with the latest theories. Where the Habitable zone will be and whether any terrestrial-type planets will be in it depends partly on how you interpret that term: consider also that some moons of Jupiter and Saturn, for example are now thought potentially life-bearing right now, for reasons independent of Solar heating.

Hope this helps a little. {The poster formerly known as 87.81.230.195} 90.197.66.165 (talk) 00:32, 9 February 2012 (UTC)

nerves to size depiction chart required

I am trying to find a chart of the human body which depicts skin area size in proportion to the richness of nerve cells in that area. Thus, for example, eyes, lips, hands and feet are shown much larger than areas such as the forearms and thighs. I remember that genitals are not depicted at all, as the testes, for example, would be the size of cannonballs! Myles325a (talk) 10:58, 8 February 2012 (UTC)

I know the picture you mean, although in the version I recall the genitals were depicted, which is what made it so striking! The closest I have been able to find so far is the cortical homunculus, but I realize that's not quite what you're looking for.--Shantavira|^{feed me} 11:50, 8 February 2012 (UTC)

Try here. Bazza (talk) 13:43, 8 February 2012 (UTC)

As for the number of nerves in the genitals, it's not particularly high. Those nerves can trigger pleasure without being very numerous. More nerves are present where needed, such as the hands, for delicate work with tools, and the lips and tongue, for separating inedible things like pits and bone fragments from our food. StuRat (talk) 20:00, 8 February 2012 (UTC)

Op myles325a back live. Thanks guys. It's called a Motor / Sensory Homonculus. I needed it for an essay I'm writing. Oh, and StuRat is probably right about the genitals, leastways for MOST guys that is. My weiner is prehensile. Myles325a (talk) 02:47, 9 February 2012 (UTC)

Well I've lived on this earth for over 50 years and I've never seen or heard of a penis that can wind itself round a branch of a tree and hold on... --TammyMoet (talk) 10:09, 9 February 2012 (UTC)

Well, now you have: Hectocotylus. StuRat (talk) 05:56, 10 February 2012 (UTC)

Unusual fungus

I took this photo today at a park in Byron Bay, NSW, Australia. I'm wondering what type of fungus it is. http://tinypic.com/r/33ur9ft/5 180.181.84.225 (talk) 12:34, 8 February 2012 (UTC)

In a very broad sense, this looks like a type of fungus called a Puffball. Beyond that, however, we'll have to wait for a proper mycologist to come and identify which type of puffball. --Jayron32 14:52, 8 February 2012 (UTC)

I'm no mycologist, but it looks pretty similar to Lycoperdon perlatum. If you upload the shot to Mushroom Observer, you're likely to get a better ID. SmartSE (talk) 15:05, 8 February 2012 (UTC)

It's clearly this type of mushroom, which is labeled as an amanita, species not specified. Looie496 (talk) 02:16, 9 February 2012 (UTC)

Oh, wait, that's your picture, isn't it? Heh. Looie496 (talk) 02:19, 9 February 2012 (UTC)

Do you mind?! I don't resemble that fungus in the slightest, 'cepting I'm white.Myles325a (talk) 02:51, 9 February 2012 (UTC)

about electrical plug

why in a electrical plug, the earthing terminal is more thicker and longer than other two terminals? — Preceding unsigned comment added by 125.19.211.130 (talk) 13:00, 8 February 2012 (UTC)

So that it will fit in the socket. 180.181.84.225 (talk) 13:04, 8 February 2012 (UTC)

...in only one direction. --184.100.88.44 (talk) 03:07, 9 February 2012 (UTC)

It longer because if an electrical lead is over tensioned and pulls away from the terminals, the last conductor you want to go open circuit is the earth. It is thicker, because one wants the earth to have the lowest residence and so a thicker and longer conductor gives you that.--Aspro (talk) 13:13, 8 February 2012 (UTC)

Can I take it your are talking about this type of plug. Both ensure that on insertion into the socket the equipment is earthed before any current can flow and that the power circuit is disconnected before earth continuity is disconnected on extraction of said plug.--Aspro (talk) 13:34, 8 February 2012 (UTC)

And on UK plug sockets, at least, the longer prong of the earth makes contact with a simple mechanism which withdraws covers from the live & neutral terminal holes. Absent the earth prong, the live and neutral remain covered and thus pretty much inaccessible. --Tagishsimon (talk) 13:37, 8 February 2012 (UTC)

Think the OP is referring not to the UK but the old UK BS 546 standard which still in existence in many parts of the world that the US Empire din'nt reach. Perhaps he can come back and elucidate.--Aspro (talk) 14:20, 8 February 2012 (UTC)

There could be all sorts of "mechanical" explanations for various modern plugs, but I think at the basic level Aspro has it right in saying that "one wants the earth to have the lowest residence and so a thicker and longer conductor gives you that." HiLo48 (talk) 20:35, 10 February 2012 (UTC)

"Resistance". Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:37, 11 February 2012 (UTC)

Earth spin redux

sir, What will happen if the speed of rotation of earth about its own axis is doubled. The distance between the sun and earth will increase or decrease? — Preceding unsigned comment added by Tobyaickara (talk • contribs) 13:39, 8 February 2012 (UTC)

See the answers where you asked this question previously. — Lomn 13:50, 8 February 2012 (UTC)

Violating the 2nd law of thermodynamics leading to violating the 1st law?

Is this true that if you can violate the 2nd law of thermodynamics, it will eventually lead to violating the 1st law?

Please tell me if this is a valid example.

You have a river flowing downstream with a turbine extracting energy from it that is 100% efficient. You then have some mechanism that brings the water downstream to the top of the river that is 100% efficient at moving that water to the top in a closed system. The turbine and the mechanism are both examples of violating the 2nd law of thermodynamics. Extracting energy from the river with the turbine is essentially extracting energy from nothing thus violating the 1st law.

Correct or incorrect? ScienceApe (talk) 16:34, 8 February 2012 (UTC)

I think a properly implemented Maxwell's Demon should violate only the second, provided that the energy it extracts comes out of the hot or cold reservoirs it creates. Wnt (talk) 18:02, 8 February 2012 (UTC)

Speaking of which, someone scroll down that article around where it mentions Atomoscience and tell me if your BSometer is in the red also. Wnt (talk) 18:06, 8 February 2012 (UTC)

I don't think it is "BS" (the main researcher seems to be a reputable academic), I just think it is a very new field that isn't notable at this stage. Therefore, I have PRODed the article. --Tango (talk) 20:00, 8 February 2012 (UTC)

Actually I meant the Maxwell's Demon article, which has a section "In 2005, Raizen and collaborators showed how to realize Maxwell's Demon for an ensemble of dilute gas-phase atoms or molecules. The new concept is a one-way wall for atoms or molecules that allows them move in one direction, but not go back. The operation of the one-way wall relies on an irreversible atomic and molecular process of absorption of a photon at a specific wavelength, followed by spontaneous emission to a different internal state. The irreversible process is coupled to a conservative force created by magnetic fields and/or light. Raizen and collaborators proposed to use the one-way wall in order to reduce the entropy of an ensemble of atoms." On a closer look I think this is legit, but just sounds like something unlikely. I think the "prod" is unfortunate, though you might have it on the merits. Wnt (talk) 20:40, 8 February 2012 (UTC)

In your scenario, the first law isn't being violated as long as the only thing the turbine powers is the pump. But if some of the turbine's power is used to power something else in addition to the pump, and the system magically didn't slow down to a stop, that would be a violation of the first law. Red Act (talk) 19:10, 8 February 2012 (UTC)

The second law of thermodynamics is a statistical result about large systems of particles that are all behaving according to more fundamental laws of physics. As long as the particles are following the more fundamental laws, then they'll probably obey the second law of thermodynamics. In a hypothetical scenario where the second law is violated, either no laws of physics are violated and you're just proposing impossibly good luck, or something more fundamental is breaking. If the scenario is constructed by breaking conservation of energy, then the first law of thermodynamics is also being broken, but there are plenty of other ways you could decide to hypothetically break physics. Rckrone (talk) 04:02, 9 February 2012 (UTC)

the role of hormones

1. What are the specific roles of hormones in spermatogenesis in a human male?
2. How can the following processes give rise to genetic variation? -fertilization and -vegetative reproduction?
3. Which type of organism will exhibit the greatest genetic variability and why? -Asexually reproducing organisms and Self-fertilizing organisms — Preceding unsigned comment added by 41.205.4.87 (talk) 18:03, 8 February 2012 (UTC)

Pardon, but this sounds like a homework question, and if so people here prefer to have students work through them on their own, at least until they get stumped and have a question of their own to ask. I've taken the liberty of adding a few Wikilinks to your question above - tell us where they fall short. Wnt (talk) 18:09, 8 February 2012 (UTC)

asexual reproduction

one way of asexual reproduction is by vegetative propagation; this implies the offspring are gotten from the parent, according to me, there should be no genetic variation between the parent and the offspring and i am unable to find how that is possible. Any contribution will be of great help!! — Preceding unsigned comment added by 41.205.4.87 (talk) 18:35, 8 February 2012 (UTC)

When a plant undergoes vegetative reproduction, you are correct, there is no significant genetic variation, and plants that depend on vegetative reproduction (e.g. strawberries and bamboo) often form clonal colonies. As for "how that is possible", we can get into what physiological traits allow for such reproduction if you like (e.g. not all plants can be grown from cuttings), but the basic idea is that, if it's possible for a certain species, then the vegetatively grown "individual" must be genetically identical to the parent, because there has been no introduction of new genetic material, and no chance for recombination. There are a few edge cases. Some plants (e.g. spider plants) naturally form chimeras, and a cutting my only have some of the genotypes present. If your question is more about evolution in a clonal organism, note that very few things solely reproduce in this manner, and usually there is some opportunity for sexual reproduction. Fun fact resulting from clonal reproduction: every granny smith or red delicious apple you've ever eaten has come from a single individual. The same genetic material is maintained by cuttings and grafting :) SemanticMantis (talk) 19:00, 8 February 2012 (UTC)

(edit conflict) Vegetative reproduction, like many types of asexual reproduction, is basically a form of cloning, or just growth (for some plants). You're right that it doesn't add genetic variation. It's never the exclusive form of reproduction — it's something that happens under specific circumstances, often stressful ones where sexual reproduction would be riskier. There is usually (always?) some other form of reproduction that introduces in genetic variation, as your reasoning would lead you to conclude. Usually when we talk about vegetative reproduction is in the context of artificial reproduction, when humans are the ones doing the cloning, and have purposefully limited sexual reproduction (with seedless varieties being the ultimate extension of this — plants which cannot self-reproduce without being cloned or grafted). --Mr.98 (talk) 19:05, 8 February 2012 (UTC)

Except that reasoning is backwards. The general wisdom, and observation, is that organisms capable of both sexual and asexual reproduction utilize the asexual variant unless they are under stress. This is certainly the case for hermaphroditic nematodes and some species of rotifer. Vertebrates capable of asexual reproduction typically do so only when there are no mates available, at least in the case of parthenogenic lizards. Someguy1221 (talk) 22:49, 8 February 2012 (UTC)

Ah, you are right. How interesting. --Mr.98 (talk) 23:42, 8 February 2012 (UTC)

And now that you mention rotifers, the Bdelloidea are certainly an edge case. All individuals are female, and they only reproduce partenogenetically. The closest they ever come to sex is incorporating random DNA when they are reanimated from a dessicated state o.O SemanticMantis (talk) 01:45, 9 February 2012 (UTC)

That is some crazy sh*t. --Mr.98 (talk) 15:16, 9 February 2012 (UTC)

Also, mutation may come into play here. Let's say one cell mutates in a way that allows it to better retain water than the others. This cell is more likely to survive and reproduce than the others during dry periods. Over time, more of the plant will be composed of such cells, and more of the new individuals that survive will be, as well. Combine this with organisms being able to select their own rate of mutation (by only having one copy of a gene or many copies, for example, or exposing the DNA to UV in sunlight), and you get a viable form of reproduction with the mutation rate fairly high. StuRat (talk) 19:53, 8 February 2012 (UTC)

I really doubt individual cell mutation has too much to do with it in complex multicellular organisms. I think you overestimate how important any individual cell can be in a positive sense. --Mr.98 (talk) 23:44, 8 February 2012 (UTC)

Plutonium inventory

Is there a good estimate on how much plutonium was produced during the runtime of all nuclear power plants since the 1940s? --Stone (talk) 20:12, 8 February 2012 (UTC)

Do you mean civilian, military, or both? Do you mean plutonium that was separated or are you including plutonium that remains in a form of waste? There are fairly nice numbers for worldwide stocks of military plutonium that was separated. There are some hand-wavy figures for plutonium content in wastes (which could be separated, but isn't). Civilian-generated plutonium is only separated in reprocessing plants, in some countries, and very careful inventories of those exist. Depending on what you're asking for specifically there are more or less better estimates, but all of it is complicated and with heavy qualifications. (e.g.) The ranges I have seen for separated plutonium are between 300-500 tonnes. I've no idea about unseparated, but it's quite large too. --Mr.98 (talk) 23:40, 8 February 2012 (UTC)

Thanks! This is exactly what I was searching for! Perfect!--Stone (talk) 18:34, 9 February 2012 (UTC)

How long does ice in the Antarctic ice sheet last

Antarctic ice sheet article states that the ice sheets began 45-34 mya. Have they mostly covered Antartica continuously since this time? (Any evidence for major periods of decline?) Also how long does it take for ice to flow from the time it was originally deposited in the interior to the time it breaks up in the ocean. How old is the oldest ice to be found there? SkyMachine ⁽⁺⁺⁾ 22:14, 8 February 2012 (UTC)

I believe most of the ice only lasts for a small fraction of that period. That is, it flows to the sea and melts and is replaced by new ice. However, there may be spots where it is prevented from flowing to the sea, such as in a volcanic caldera, where the ice may be much older. StuRat (talk) 23:03, 8 February 2012 (UTC)

Indeed, even the lowest portions of the oldest ice cores are believed to be less than 1 million years old. Someguy1221 (talk) 23:09, 8 February 2012 (UTC)

Some of the oldest ice on the continent is believed to come from the Antarctic dry valleys, where claims of ice (usually mixed with soil) up to 8 million years in age have been made. Most of the ice on the continent is far younger though as the large ice sheets slowly flow towards the oceans and carry much of the oldest ice out to sea. The oldest reliably dated ice from ice cores on the ice sheet are about 800000 years old. There is speculation that some of the ice at the base of the ice sheet is older, perhaps 1.2 million, but basal ice tends to be highly disturbed by turbulent flow and/or basal melting, which makes it very difficult to date reliably. Dragons flight (talk) 21:05, 9 February 2012 (UTC)

Brain and learning

Is there a certain part of the brain responsible for human capability of learning? If so, does this part of the brain also affect other things? Thanks! 64.229.180.189 (talk) 23:47, 8 February 2012 (UTC)

More than one part of the brain, since there's more than one type of learning. Learning how to walk, for example, is quite distinct from learning the capital of North Dakota. Perhaps the better question would be if there are parts of the brain which don't learn, that is, which operate on instinct alone. I believe so, such as the brain stem, which regulates breathing and heartbeats, neither of which needs to be learned. Portions related to the senses are a mixed bag, as the parts that process the images, smells, sounds, etc., initially don't require learning, but the associations with events, objects, dangers, etc., do. StuRat (talk) 00:17, 9 February 2012 (UTC)

See long term potentiation for a major variety of learning; see the hippocampus for a major seat of memory. Wnt (talk) 15:00, 9 February 2012 (UTC)

February 9

Ionic gases

When an ionic compound is vaporised, does it form individual molecules or does it separate into its component ions? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 01:24, 9 February 2012 (UTC)

Stays as molecules, like water vapor. StuRat (talk) 01:26, 9 February 2012 (UTC)

Water is covalently bonded. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 03:30, 9 February 2012 (UTC)

Just to correct Stu, in the solid phase, there is no such thing as an ionic molecule. Sodium chloride doesn't form molecules in the solid phase. In something like Ionic liquids, the situation is complex, but roughly speaking the individual ions are free moving, though they can group up in molecule-like structures. Ionic gases form ion pairs or complexes which behave kinda like molecules, near as I can find from a quick literature review. Such clusters are called "molecules", except that they are held together purely by the electrostatic interaction of the positive and negative ions. See this paper from 1951 which gives an overview. If heated enough, such an ionic gas may form a plasma as the individual ions are seperated. --Jayron32 04:44, 9 February 2012 (UTC)

Did I say anything about the solid phase ? I just said that ionic particles stay bonded, just like water vapor (which is covalently bonded) does. And, of course, I was assuming conditions short of those needed to form a plasma. StuRat (talk) 04:53, 9 February 2012 (UTC)

In sodium chloride gas, there are weakly bonded polar molecules. This gas consists of a mixture Na, NaCl, Na₂, Na₂Cl, Cl, NaCl₂ and a variety of other shortlived species. Upon collision, individual molecules always exchange partners. Plasmic Physics (talk) 01:01, 10 February 2012 (UTC)

The percentage of DNA sharing in Monozygotic twins

what is the "exact" percentage? (if known), and, could be variants? thanks. — Preceding unsigned comment added by 81.218.145.251 (talk) 03:43, 9 February 2012 (UTC)

Almost 100%. At least a handful of mutations will inevitably occur prior to the splitting of the embryo. Even if the split occurred at the two cell stage, one would expect genetic variance of 1 part per billion (99.9999999% identicalness, if that's a word). In practice, copy number variation has been observed between "identical" twins, as well as variation in DNA methylation patterns. Someguy1221 (talk) 03:52, 9 February 2012 (UTC)

Could someone please draw up a schematic of an obvicopter?

Or link one if it already exists?

Some Californian Hispanic dude named "Juan Carlos" drops the term "obvicopters" occasionally - "Can't hear, obvicopters too loud," "...it is ##obvicopters," etc. Another user around him stated that their engine sound would sound slightly different from the helicopters'.

How would an obvicopter be built differently? Is it, perhaps, the mystery jet-run tilt-rotor craft seen in the film, I, Robot?

Apparently it's a concept helicopter that isn't in full production yet, but Google seems to prefer to keep it under wraps. _{Perhaps under government order to keep it classified...}

Or it's not forthcoming for other reasons. Anyway, what could you dig up about this? --70.179.174.101 (talk) 11:47, 9 February 2012 (UTC)

It seems fairly obvious you're referring to Meta:Foundation wiki feedback/Archive/2011#Talk:Staff, Meta:IRC office hours/Office hours 2011-02-11, [3] (connection between names apparently self disclosed on publicly logged IRC channels Meta:IRC office hours/Office hours 2012-01-20) so why don't you just ask user:killiondude rather then coming up with another random wacky conspiracy theory? Seems fairly likely it's a joke, although it wouldn't surprise me if the joke continues if you indicate you think it's otherwise as done so here. Nil Einne (talk) 14:48, 9 February 2012 (UTC)

Guessing, based on Nil Einne's provided information: "Obvi-" looks to be "obvious". "-copter" is a throwaway. The statement is a jesting reply to a correction: "I can pretend I didn't hear that, so I can pretend I wasn't wrong / didn't make that mistake / have eleventy billion dollars." Should killiondude appear and clarify, the obvicopters will no doubt be flying low over my area. — Lomn 15:21, 9 February 2012 (UTC)

It's probably derived somewhat from roflcopter, an undoubtedly hilarious internet meme of times gone by. - Cucumber Mike (talk) 16:09, 9 February 2012 (UTC)

Is his accent that thick or do you mean Ornithopter? (Juan's email address is also Ornithopterman@ ------.com). Sound-wise, if a helicopter goes thwhaat-thwaat-thwaat then a ornithopter goes more like whaap-whaap-whaap-whaap. The air flowing over the rotor blades of a heli is accelerated to much higher speeds, hence the sharper attack and decay of the beats. The engines should not (as far as I can make out) sound any different. Maybe he is just talking simply. --Aspro (talk) 21:11, 9 February 2012 (UTC)

I see the Reference Desk continues its celebrated tradition of indulging in trolls. It's just a meme that I did not initiate but did perpetuate. Killiondude (talk) 22:57, 9 February 2012 (UTC)

Do permanent magnets generate heat at all?

I had someone argue with me that if you use a permanent magnet to "launch" a projectile (in space), it would not generate any heat. I'm not entirely sure what the hell he was talking about, but I wanted to confirm if his claim was true or not. ScienceApe (talk) 13:31, 9 February 2012 (UTC)

Magnets are not magical physics-violating devices, and byproduct heat results from all useful work, per the second law of thermodynamics. — Lomn 14:30, 9 February 2012 (UTC)

Launching a projectile into space with a permanent magnet would be quite a feat, unless you live on an asteroid. But there should be some heat from eddy currents in any changing magnetic field. Wnt (talk) 14:58, 9 February 2012 (UTC)

That's what I thought, thanks. ScienceApe (talk) 21:27, 9 February 2012 (UTC)

question about plutonium

I've seen pictures on the Internet of workers holding objects such as the plutonium buttons and working directly in front of weapons grade plutonium. How is this possible because during Chernobyl people would die from radiation exposure just from looking briefly at the plutonium rods. --208.83.61.116 (talk) 17:43, 9 February 2012 (UTC)

Plutonium-238 decays by alpha decay. Alpha particles are blocked by very little material (see alpha decay#Toxicity), so it's pretty safe to handle (when it's in a big block; you wouldn't want to be breathing or drinking this stuff). Other radionuclides decay by gamma emission, which is very penetrative. Used nuclear fuel elements, such as one would find in an burning reactor, contain a variety of daughter products, of which plutonium is one of the lesser hazards. -- Finlay McWalterჷTalk 18:14, 9 February 2012 (UTC)

You may find Chernobyl#Radioactive release useful. It says, among other things: "While the general population often perceives plutonium as a particularly dangerous nuclear fuel, its effects are almost eclipsed by those of its fission products." --Tango (talk) 18:47, 9 February 2012 (UTC)

The fuel rods used uranium, not plutonium, although there was plutonium present as a consequence of the nuclear reactions. As others point out, irradiated fuel rods are dangerous to directly observe (through air - water of sufficient depth is a good shield) due to radiation created by decay products, not because of inherent danger posed by uranium or plutonium, which can be handled with due precaution. I believe Richard Rhodes described a piece of plutonium in The Making of the Atomic Bomb that when handled (with gloves) was warm, rather like a live rabbit. Short exposure, and avoidance of ingestion, is not particularly perilous. Acroterion (talk) 18:55, 9 February 2012 (UTC)

I suspect that in almost all cases of the photos of people handling plutonium, the people are working with glove boxes. (E.g. This guy.) That means they're behind glass. I've never seen any where there wasn't a glovebox, anyway. or some kind of containment (e.g. even just a plastic bag, much less more complicated shielding devices).

But in any event, the main exposure-based health hazard from plutonium is through inhalation. Most plutonium in the real world, if not in a glove box, is either coated in something or is not handled except with gloves and by people trained to handle it. It's not particularly radioactive in and of itself, compared with the sorts of things that are inside of a working nuclear reactor (where the problem are the fission products, which are highly radioactive). But still, people are on the whole pretty careful in how they handle plutonium, though if you aren't aware that these photos are generally taken in glove boxes, I could see you thinking people were being rather cavalier about it. --Mr.98 (talk) 01:42, 10 February 2012 (UTC)

About Chernobyl, people did not fall over dead from looking at rods. 31 people died in the three months after the event - mainly from radiation from breathing the smoke. See also Acute radiation syndrome. 75.41.110.200 (talk) 05:06, 10 February 2012 (UTC)

Though physical proximity to unshielded control rods does expose one to a lot of radiation, even without the added issue of inhaling radioactive particles. But yes, "looking at" states that poorly. --Mr.98 (talk) 13:58, 10 February 2012 (UTC)

Human hair

Does an adult's body need some DHL for living healthily? If I would cut a hair off completely(even under the skin without the root), how much time it will take for it to grow up beyoned the scalp? — Preceding unsigned comment added by 87.68.222.18 (talk) 21:29, 9 February 2012 (UTC)

I'm guessing you don't mean the parcel company, but that's all Google, Wikipedia and Wiktionary can find with that acronym... --Tango (talk) 22:32, 9 February 2012 (UTC)

Nothing that acronymfinder.com brings up seems appropriate, though I am intrigued by "Dynamic Head Loading". Anybody know what that is? Clarityfiend (talk) 22:43, 9 February 2012 (UTC)

A pubmed search for "DHL nutrition" gives one, irrelevant hit (with DHL being part of the name of a cell line). Human hair grows by about 1.25 cm per month, see Human hair growth. --NorwegianBlue ^talk 23:16, 9 February 2012 (UTC)

Is it possible the OP means Docosahexaenoic acid (DHA) and is remembering wrong? DHA seems to be a common supplement and is evidentally sometimes marketed to reduce hair loss, although it's not clear to me that OP was suggesting 'DHL' was needed for anything related to hair anyway. Nil Einne (talk) 23:37, 9 February 2012 (UTC)

Or maybe they mean DHT (dihydrotestosterone) ? StuRat (talk) 05:48, 10 February 2012 (UTC)

I thought of that but it's definitely not something many people should be taking even if they have it naturally present. Nil Einne (talk) 09:40, 10 February 2012 (UTC)

But they didn't ask if they should take it, only if the human body needs it. StuRat (talk) 19:18, 10 February 2012 (UTC)

Yes but if it's not something you consume in some way, the meaning of 'need some ... for living healthily' is questionable. Nil Einne (talk) 14:00, 11 February 2012 (UTC)

Based on his follow-up post below Wikipedia:Reference_desk/Science#Dihydrotestosterone, it looks like I guessed right. Let's close this Q and answer below. StuRat (talk) 05:16, 12 February 2012 (UTC)

Resolved

February 10

Meter definition

i read that the definition of metre is "The metre is the length of the path traveled by light in vacuum during a time interval of 1⁄299792458 of a second." Why not define metre as 1/300,000,000 of a second so that speed of light will be exactly 300,000,000m/s? MahAdik _usap 01:05, 10 February 2012 (UTC)

Because, as Metre#Meridional definition states, it was not defined in terms of the speed of light originally, but rather as "one ten-millionth of the length of the Earth's meridian along a quadrant". It's a little too late to go changing it now. Clarityfiend (talk) 01:13, 10 February 2012 (UTC)

(ec) Because the meter (and the second, and the gram) already had a widely-implemented physical meaning prior to defining it in terms of the speed of light. Switching its size capriciously would create untold havoc and inconvenience for very little gain. Instead, the speed of light definition ties an existing value to a physical constant. — Lomn 01:14, 10 February 2012 (UTC)

The key issue is that, while 300 000 000 m/s and 299 792 458 m/s only differ by less than one part in a thousand, when the definition of a meter was set to the 1⁄299792458 of a second definition in 1983, people were already using the meter, and were able to accurately measure distances with much greater accuracy than one part in a thousand. (Which isn't actually that hard, as the difference between the two meters is about 0.7 (current) mm - a difference that's visible to the naked eye.) While ponderously slow about it, the international metrology community is perfectly willing to redefine units (see New SI definitions) however, the key consideration in all such changes is that the old and new units must match up to within the error for even the most accurate measurements. That is, if something measured 10245.6±0.3 mm prior to the redefinition, it should measure 10245.6±0.3 mm after the definition. To do otherwise invites confusion as you'd constantly have to check the publication date of books, references, etc. to see if they were measuring things with the old meter or the new meter. -- 67.40.215.173 (talk) 17:03, 10 February 2012 (UTC)

BOMA

Crossword Clue : Anaconda Answer Given.  : Boma.

Nowhere can I find any mention of, or reference to, the word BOMA in any capacity much less to connect with Anacona. Can you help me - I hate words I cannot explain. My, hopeful, thanks - J. Mumvonston (talk) 02:40, 10 February 2012 (UTC)

Googling for those two terms finds many hits. The first two are "boma" in a Scrabble dictionary and a work by Richard Price (American anthropologist) about explorers in Suriname. Each one gives them as synonymous or a cross-breed or more specific type or something like that. DMacks (talk) 02:48, 10 February 2012 (UTC)

The OED has it: bom or boma - "The name in Congo, W. Africa, of ‘a huge non-poisonous snake swallowing deer, etc.’ (see Merolla, Vocab.; Proyart; Cavazzi Congo, Matamba, & Angola; Magyar Süd-Afrika). Apparently carried by the Portuguese from Congo to Brazil (Roquete has bom bôma ‘serpent d'Angola et du Brésil’), and there applied to the largest boas, in which sense it appears in some English works. (The history has been traced for us by Dr. E. B. Tylor.)" (Oops, forgot to sign.)--Rallette (talk) 08:31, 10 February 2012 (UTC)

Electronic color code

May I know how to distinguish colour coding for 5 bands described by this article from the same colour coding used by some commercial vendors such as [4].--Almuhammedi (talk) 08:35, 10 February 2012 (UTC)

As far as I can tell, that coding schemes are completely compatible. The second one simply lists extra colors for the fifth band that aren't even used in military applications. (Unless the US military color-coding chart I found is simply incomplete.) Someguy1221 (talk) 10:09, 10 February 2012 (UTC)

It's been a long time since I worked on any Defence Work but I think I have found an inaccuracy in the WP article Electronic color code ( apart from they don't know how to spell colour of course) which doesn’t ring true. It states: ”Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability); refer to MIL-HDBK-199 for further details.” Reliability? This sounds like nonsense. If one wants the resistor to last and not fail too soon, one simply chooses a resistor with a high wattage rating. Doubling it is a good rule of thumb but one need to consider the ambient temperature also –so in the case of (say) a missile, where air friction is going to heat the interior up, one might want to calculate a high value still -there are handy graphs provided by the manufacturer to avoid doing the sums). As for 5 band resistor colour codes (and the military certainly do uses them), this chart explains it well. [5]

So 15K Ω example in the above chart put simply:

1 (brown)

5 (green)

0 (black)

00 (green)

-------------------

=15000 Ω

@ 1 % tolerance (brown)

As a certain meerkat might say : Simples! --Aspro (talk) 23:14, 11 February 2012 (UTC)

Permission

Dear Sirs My colleague Rex Palmer and I are preparing a 5th edition of "Structure Determination by X-ray Crystallography". We would be grateful for permission to reproduce the top right-hand two Wikipedia figures that appear under "Penrose Tiling!. Yours sincerely Mark Ladd & pp Rex Palmer — Preceding unsigned comment added by Kramdaal (talk • contribs) 10:13, 10 February 2012 (UTC)

The article in question is Penrose tiling. Do you mean the two pictures - File:Penrose Tiling (Rhombi).svg and File:RogerPenroseTileTAMU2010.jpg? Wikipedia doesn't own those pictures, and so can't grant you anything. The diagram is in the public domain, but the photo was uploaded by Solarflare100. That was Solarflare100's only contribution, so I know of no way to contact them. -- Finlay McWalterჷTalk 10:25, 10 February 2012 (UTC)

However Wikipedia:Reusing Wikipedia content and Commons:Commons:Reusing content outside Wikimedia should provide you some idea how you may be able to reuse the content without further permission of the copyright holder. Bear in mind this is not intended to be legal advice and we cannot guarantee the copyright situation of either image is as suggested in the file description. Nil Einne (talk) 15:49, 10 February 2012 (UTC)

You should probably discuss with your publisher about what licensing rules they have. The licenses on the two images in question are clearly marked: this one was released into the public domain by its copyright holder, and this one is licensed for free re-use under the Creative Commons "Attribution 3.0 Unported (CC BY 3.0)" license. Your publisher will probably know whether such content is acceptable for their uses. Nimur (talk) 19:19, 10 February 2012 (UTC)

UV light from sun

Our article on vitamin D says that humans only make vitamin D when the UV index is above 3. Assuming someone standing directly in the sun with no cloud cover, roughly what angle of the sun with the horizon is that equivalent to? And is there a website that you can stick your location or even just latitude in, and it tells you what hours and days the sun is above that angle? I assume such things must be possible, because our articles seem to talk about different places having strong enough sunlight for given percentages of the year. 86.163.211.160 (talk) 14:06, 10 February 2012 (UTC)

You do know that you can get vitamin D from vitamin pills or foods and beverages supplemented with it, right ? Considering the damage UV causes to the skin, this is the safer approach. StuRat (talk) 19:13, 10 February 2012 (UTC)

Apparently sunscreen or other sunlight denial has not proved itself as an unmixed blessing. (See PMID 8475009) It should be very surprising to me if humans truly suffer from an appropriate level of exposure to the Earth's sun. Wnt (talk) 20:45, 10 February 2012 (UTC)

A couple questions about that study:

1) Did they eliminate vitamin D deficiency by comparing those with sunlight exposure with those taking vitamin D ?

2) People who get more sunlight exposure may also get more exercise (the outdoorsy type of people). Did they control for this variable ? StuRat (talk) 20:55, 10 February 2012 (UTC)

I'm not especially interested in what various unqualified people think about appropriate sources of vitamin D (this, and the dangers of sunlight, attracts a lot of crank views for some reason, and I don't really want to play that game). I'm really interested in being able to look at when there is strong enough sunlight to make vitamin D, in different parts of the world. I assume such a thing is achievable, and given the various interests it seem like something that would be a widget on a website somewhere. Is this so? 86.163.211.160 (talk) 23:06, 10 February 2012 (UTC)

I won't offer an unqualified opinion on the Solar altitude, but will mention that air quality may also be an important factor: even on a cloud-free day, the degree of various pollutants in the air may, I suspect, greatly influence how much UV gets to the ground. {The poster formerly known as 87.81.230.195} 90.197.66.183 (talk) 00:48, 11 February 2012 (UTC)

Such a widget to compute the U index is undoubtably possible. Its really just the same as what experts have come up with for the photo-voltaic (solar panels) industry to predict power output of solar panels. But I doubt that it would be any practical value. Vitamin research is notoriously shakey, and requirements will vary from race to race and person to person. I've never seen it cited anywhere what area of skin is required to be exposed to maintain a given vitamin level at a given UV index, and that is surely a valid and important question. Keit120.145.158.234 (talk) 02:59, 11 February 2012 (UTC)

Let me first note that the UV index is defined as a measure of UV exposure at noon, so it is not a simple measure of UV exposure as a function of sun angle. With that being said, it seems to be difficult to give an authoritative answer to the question in terms. Calculating the UV index requires having a "radiative transfer model", a mathematical formula for the amount of UV light that reaches the ground at each frequency for a range of parameters, and it seems that each agency that calculates UV indices uses its own idiosyncratic transfer model. According to this paper, vitamin D production in the skin begins when the sun is around 20-30 degrees above the horizon. Looie496 (talk) 03:12, 11 February 2012 (UTC)

Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation

From an astronomy/sunlight perspective this on-line calculator may help with what you're looking for. When trying to determine how much UV gets through, the transmittance of the atmosphere to UV is quite low, so you'll need to think about path lengths, attenuation and the Beer–Lambert law. LukeSurl ^{t c} 11:10, 11 February 2012 (UTC)

Hemoptysis

Hello. Can Hemoptysis result from flu, or flu-like conditions? (Before some zealot removes this question, please note that it is just a general medical question, and that I am not asking for a medical diagnosis, and don't want one, either. Thank you). Polisher of Cobwebs (talk) 18:59, 10 February 2012 (UTC)

Any condition which causes a sore throat could cause blood to be coughed up from the esophagus. However, hemoptysis doesn't include that. It does include blood from the trachea, but if the patient has an infected trachea, that might then be classified as pneumonia. StuRat (talk) 19:10, 10 February 2012 (UTC)

Age and intelligence

At what age do humans reach the maximum capacity for learning ? (Note that this should be earlier than the age at which they attain the maximum amount of knowledge, since there is a substantial delay between obtaining the capacity to learn and absorbing all the information possible.) StuRat (talk) 19:22, 10 February 2012 (UTC)

What makes you think there is a "maximum capacity for learning"? The brain is not a bucket. It is not a hard drive. It is a complicated living organ. Over time, various parts of it have increased ability (e.g. language sparks up in an incredible way when very young), and some parts decline over time, but I'm not sure how one correlates that with a singular notion of a "maximum capacity for learning." I don't know if the processes described on this page are correct or not, but it points out what a more nuanced analysis of age and learning might look at. --Mr.98 (talk) 20:04, 10 February 2012 (UTC)

The Aging brain article might help answer this question. Mitch Ames (talk) 11:31, 11 February 2012 (UTC)

There's a sentence about this in the IQ article, which can be found by searching for the phrase "age 26". You'd still keep gaining knowledge and experience for decades afterwards though. Sagittarian Milky Way (talk) 19:35, 11 February 2012 (UTC)

Relativistic (polar) jet directed in one direction

It seems that the Messier 87's jet is going only in one direction while other jets as seen in Bipolar outflow seem to go in two opposite directions. The article on relativistic jets seems to indicate that jets from black holes can also go in two directions. What causes the jet to either go in one or two directions? ScienceApe (talk) 20:53, 10 February 2012 (UTC)

That's explained in the article Relativistic_beaming (found via M87#Jet...) --Wrongfilter (talk) 20:59, 10 February 2012 (UTC)

As a physicist, I would simply say "this behavior is obviously caused by an asymmetry in the physical system." Isn't it obvious? The interesting follow-up question is, of course: is this a fundamental asymmetry of the process (which has universal cosmological implications), or is it simply due to initial inhomogeneity (i.e., did the accreted dust-cloud have a net initial angular momentum)? Here's a nice web-page from UCLA, on cosmological anisotropy and inhomogeneity, and here's an online text from CalTech, specifically discussing velocity inhomogeneity in M87. As an engineer, I'd just say, "... there's probably a second jet we just can't see from Earth. Either way, the experts have chimed in with their opinions; the M87 radio jet is quite famous. Nimur (talk) 22:08, 10 February 2012 (UTC)

Obvious? What's obvious about it? @_@ I hope that was a joke.. Not all of us are physicists, I'm just a layman. ScienceApe (talk) 23:57, 10 February 2012 (UTC)

(It was a physicist joke, sorry if it was lost on the uninitiated). Nimur (talk) 00:26, 11 February 2012 (UTC)

Related question, if the single jet is just an optical illusion, and there's really two jets, is it possible for there to be just one jet? ScienceApe (talk) 00:02, 11 February 2012 (UTC)

This is, essentially, the crux the links I posted. The answer is, "it's hotly debated, because the observational evidence is still fuzzy enough that either answer makes sense." We don't really know whether the other jet exists (and is invisible); or if it doesn't exist, and there's some interesting physics happening. Nimur (talk) 00:29, 11 February 2012 (UTC)

How much processing power would be needed to emulate a 4D visual cortex?

That would be as good in 4D space as a human visual cortex is in 3D space. How many rods and cones would 3D retinas need to get similar resolution and field of view? 1 trillion? (100 million^3/2) How many kilograms would it weigh if built out of neurons (in 3D space)? (and presumably would need to be fed Matrix-style to run as the requisite 4D eyeball is not in existance). Since I read that even the current neuron-based paradigm is close to limits of intelligence (tradeoff of wiring thinness vs. transmission quickness and energy usage) then this number might be ridiculouly high or maybe impossible. On the other hand, how well would a current visual cortex do if rewired for 4D space? Not very well I suppose? Sagittarian Milky Way (talk) 22:35, 10 February 2012 (UTC)

I guess from teh way you worded it that you did not consider time as the 4th dimension, as is sometimes done. This question can be answered in two ways:-

1) The question is not a valid question because systems of greater than 3 dimensions are mathematical constructs useful in certain fields and do not represent any physical reality.

2) No increase in retina sensors and no increase in brain neurons would be necessary. This may surprise you, but there are good reasons as follows: We don't see like a televion camera - most of the information from our retinas is thrown away on the path to conscious vision. The brain selectively, depending on the merits of the scene and what you are looking for, "focusses" on only a limitted subset of visual information, and reconstructs what you consciously see or think you see. This is easily demonstrated with optical illusions. So if you get 4D eyes, the brain can still throw most of the info away and reconstruct. We don't actually see in full 3D, its more like enhanced 2D, as demonstrated by the long success of 2D representations in printed matter and movies, and perhaps the success of 3D enhancemnt to movies shot in 2D (eg Titanic). Also, human vison is essentially with 3 primary colours - red, green, and blue. Most birds insects have 4 primary colours - red, green, blue, and ultravioet, and dogs sort of 2 and a bit. An extra primary colour is potentially adding information just as an extra dimension would, but in fact its just a re-allocation of a portion of rods and cones or sensor cells to a different colour. But researches have in certain animals manipulated the genetic expression of retinal cells to add a primary colour. They fould that the standard brain adapted and coped just fine. So it should also cope with an extra dimension. As I recall, this was covered in a recent Scientific American article. Keit120.145.158.234 (talk) 02:35, 11 February 2012 (UTC)

Visualizing point data

Does there exist software which would allow me to view point clouds (at least XYZ, possibly XYZ+colour) and measure distances between points? e.g. so I can measure the approximate distance between two walls in a model. Thanks! 131.111.255.9 (talk) 22:44, 10 February 2012 (UTC)

Certainly, pretty much any 3D CAD system will do that, although it's quite difficult to visualize 3D points. Some type of motion (rotation or Z-clipping as you move through the point field) or connections drawn between them (like constellations) can help. (Z-clipping is where the parts of the object closer to you are hidden so you can see the parts farther away.) Otherwise, the usual cues for telling which objects are closer and which are farther don't work with points. I suppose you could have them be little spheres or cubes, in a perspective view, so they do get larger as you get closer. You could also use color, where points farther away become darker and bluer colors, like distant mountains. StuRat (talk) 22:48, 10 February 2012 (UTC)

For a free, open source option, Octave can do that. It has MATLAB style syntax, and uses gnuplot for a variety of visualization techniques. SemanticMantis (talk) 23:19, 10 February 2012 (UTC)

Thanks. Octave might do the trick, although I was hoping for more of a 'prepackaged' solution - perhaps from the GIS field. I shall have a look! 131.111.255.9 (talk) 03:45, 11 February 2012 (UTC)

Astronomy stuffs

For number 18, the answer is ultra light. I want to know the relationship between temperature and wavelength range. And a brief description of wavelength for each of the answer.

For number 19, the answer is 4 times more. I don't really understand how they got it. So basically if what is the relationship between angular diameter and amount of energy it radiates and its wavelength. So if i was given 2 out of 3 i can figure out the last one. And don't ask me why i didn't ask my teacher. This is not part of my classes. Thanks.Pendragon5 (talk) 23:21, 10 February 2012 (UTC)

Wien's displacement law will give you a relation between peak blackbody-wavelength and temperature. The Stefan–Boltzmann law will give you a relation between temperature and the rate of energy radiated (per area or per solid angle, depending on the formula you choose to use). By stringing these two equations together with a bit of algebra, you can calculate the total energy radiated, if you know the size of the objects. Whether these laws are a good approximation for your object will depend on how accurately you need to calculate: there are loads of empirical adjustment "fudge factors" - like "grey body radiation;" and my personal favorite astrophysical fudge factor - whether the radiant antenna temperature of the universe is 0 or 4 kelvins. (Properly, you should modify Stefan Boltzmann equation to account for this, but in practice it makes almost no difference when you are considering stellar radiation). And for the true astrophysical pedant, 4 kelvin isn't accurate enough; you should actually calculate the impedance-matching for every single emitted photon wavelength to the color temperature of the universe, lest you calculate a miniscule error on the radiated power that is far below any realistic noise-floor. (As an addendum, I'll just comment that our cosmic microwave background radiation article cites recent COBE measurements of the blackbody temperature as "2.725 K" with error-bars too small to mention. I still always use 4 K, and it's never interfered with any of my work so far). Nimur (talk) 00:49, 11 February 2012 (UTC)

2.8977685(51)×10−3 What is the (51) mean? And when i plug it in my calculator. For the temperature, do i put 8,500 or 8,500,000? Pendragon5 (talk) 01:06, 11 February 2012 (UTC)

Alright never mind. Base off from the answer i got, it all makes sense now. Let me put it out here and can you tell me if i did it correctly ok? So let put 2.8977685 X 10^-3/8,500= 3 X 10^-7. Ultra violet range is from 1 X 10^-8 to 1 X 10^-7. So 3 X 10^-7 is in that range so that's why the answer is ultra violet right?Pendragon5 (talk) 01:20, 11 February 2012 (UTC)

Almost, except 3x10^-7 is greater than 1x10^-7, so it isn't actually in that range. The first sentence of ultraviolet says it goes up to 4x10^-7, though, so it in the range, the range is just a little bigger than you thought. --Tango (talk) 01:27, 11 February 2012 (UTC)

Oh yea ops. I meant 4 X 10^-7.Pendragon5 (talk) 20:27, 11 February 2012 (UTC)

The (51) is a short way of saying +/- 0.0000051, ie. it's the uncertainty in the last two digits of the main number. K means Kelvin, not thousand. --Tango (talk) 01:22, 11 February 2012 (UTC)

Oh wow pretty useless then. I'm looking for the rough estimate is good enough. On number 19 i'm still lost on how to do it. How am i going to calculate the energy of Star F and E then compare them? Thanks.Pendragon5 (talk) 01:31, 11 February 2012 (UTC)

Never mind. I have figured out how. Thanks for pointing out directions for me in the first place :D.Pendragon5 (talk) 04:09, 11 February 2012 (UTC)

Light

If for example humans evolve w/o the sense of sight, can we come up with theories about light? MahAdik _usap 23:53, 10 February 2012 (UTC)

I suppose so. After all, we are able to come up with theories to explain X-rays, and we can't see those. Sound is not as similar as X-rays, but still somewhat similar to light, so, once we explained that, we would have a head start towards explaining light. StuRat (talk) 00:00, 11 February 2012 (UTC)

Can you think of a scenario where we will be curious about light? MahAdik _usap 00:32, 11 February 2012 (UTC)

Even a blind man finds relief in the shade. -- 182.232.144.48 (talk) 04:17, 11 February 2012 (UTC)

It is a weird question but i suppose pretty interesting. We can't see anything then we must have developed some special kinds of functions that don't require the sense of sight to do all the things humans have accomplished until to this day. If we don't have any special function to interchange with the sense of light then i suppose we probably are still stay at same as cavemen. And by the way, you don't need to see or hear or sense something to understand it. What makes us special is our conscious and imagination, which are far more important than knowledge. Knowledge is already there, you just have to learn it. But to invent, motivate, something new... like a theory or new technology... A lot of people can learn but not many have rich imagination such as Albert Einstein. As smart as Einstein has said once: "Imagination is more important than knowledge", which is really true when i think about it.Pendragon5 (talk) 00:42, 11 February 2012 (UTC)

And in human history, there are A LOT of predictions and theories through out human history about something that we don't even understand it yet but with our imagination we can come out with something that makes sense. I'm really astonished that people thousands years ago already have richer imagination than me. Imagination is something that has no limit and infinite of possibilities. And later on, when we are advanced enough then we can confirm it. Not all of them were correct though, just some of them. Predictions and theories came first then the confirmation comes later, it may take few years up to hundreds or thousands of years to confirm them.Pendragon5 (talk) 00:48, 11 February 2012 (UTC)

(edit conflict) Einstein is what im thinking when i asked this question, i just thought that if we cannot percieve light, then we wont have much understanding about it, then we wont be able to formulate a good explanation for gravity, im just thinking that if its true, then maybe their some forces that we cant percieve right now that might help us explain the universe and i hope i am making sense MahAdik _usap 01:06, 11 February 2012 (UTC)

We better try to predict those forces now and let wait until we are advanced enough to find them out. But as always the first step is to predict and choose the correct direction.Pendragon5 (talk) 01:13, 11 February 2012 (UTC)

Regardless of the environment, some method of creating heat would eventually be riddled out (mechanical friction, combustion, something). The transmission of heat by thermal radiation in the infrared would then be hard to miss except in the most exotic environments. Once infrared is known, curiosity would eventually follow it up to wavelengths we regard as visible. Wnt (talk) 07:57, 11 February 2012 (UTC)

If one is conceptualising a physical phenomenon for which humans have no ability to naturally sense directly or even indirectly, one may consider neutrinos. One a practical level we have no interactions with these particles. For much of human history we were simply unaware of their existence, and our theories of the universe didn't include them. However eventually as our understanding of the universe grew, Wolfgang Pauli saw a need for them in our theories, and in 1956 they were detected. There are other concepts in physics which have been theorised but not yet observed, and I'm sure there are things that exist that we haven't even thought of yet. That said, a conceptualised phenomenon that would have absolutely no interaction with us or anything we can observe, and thus be completely undetectable, is essentially indistinguishable from fiction. LukeSurl ^{t c} 11:27, 11 February 2012 (UTC)

February 11

Average lifespan of the stars

What is an average lifespan for the stars in the universe. I also want to know the relationship between mass and lifespan. According to this , our sun has 1 solar mass and its lifespan is about 10 billion. So if a star has 2 solar mass and so on or has less than .9 solar mass and so on. What are their expectancy lifespan?Pendragon5 (talk) 01:37, 11 February 2012 (UTC)

Never mind, i think i have found an awesome data table of it.Pendragon5 (talk) 01:52, 11 February 2012 (UTC)

Note that you would get a very different answer if you averaged by number of stars or by mass of stars. StuRat (talk) 01:57, 11 February 2012 (UTC)

Valence of argon in argon fluorohydride

What is the valence of argon in HArF (argon fluorohydride)? Until recently Wikipedia stated the maximum valence of argon to be 0, but R8R Gtrs tells me that it should be +2. Double sharp (talk) 02:07, 11 February 2012 (UTC)

• Well, if argon is indeed forming covalent bonds with both H and F, then the valence of Ar there is, by definition, 2 (note that this is not the name as having a +2 charge). Considering this molecule breaks apart at temperatures above -256°C, I think it's still safe to consider Argon to have max valence 0 for any practical purpose. LukeSurl ^{t c} 13:11, 11 February 2012 (UTC)

Why do we find baby animals cute?

Has there ever been an attempt to explain why humans find baby animals cute, particularly babies of other mammals? HiLo48 (talk) 02:51, 11 February 2012 (UTC)

I'm guessing there'll be some info at neoteny, though I don't know how much or how specific to your question. --Trovatore (talk) 02:52, 11 February 2012 (UTC)

The evolutionary adaptation is that we think our babies are cute so we will take care of them. By transference, the baby-like features of other animals (whether juvenile or adult) trigger the same response. StuRat (talk) 03:30, 11 February 2012 (UTC)

Yeah, I get the idea that it's good for humanity to find its own babies cute. But why the other animals? Personally, I reckon some human babies are pretty ugly, but every puppy is cute. As an Australian, I think about our native marsupial babies. Cute as all heck (I really must upload my baby wombat pics), but humans evolved on completely different continents. Why should we care? HiLo48 (talk) 03:38, 11 February 2012 (UTC)

I just noticed that wombat sounds a lot like womp rat. Coincidence? --Trovatore (talk) 03:43, 11 February 2012 (UTC)

Probably just a coincidence. But thank you for causing me to become educated about womp rats. HiLo48 (talk) 04:17, 11 February 2012 (UTC)

A baby kangaroo is not cute. Mitch Ames (talk) 11:26, 11 February 2012 (UTC)

I totally agree. The marsupial stage kangaroo is kinda nasty. When they're hopping around though, they get cuter. Shadowjams (talk) 18:00, 12 February 2012 (UTC)

Like HiLo is getting at, you'd think we evolved to find cuteness in human baby traits, but in reality, the traits we evolved to find cute are very general. An inability to move easily on one's own, small size, big round eyes, certain noises. And there would have been little need to evolve more specificity on that. It's not like a tiger mother would have let you waltz up and take her pups. Heck, maybe we find baby animals cute just to keep us from attacking them and incurring their mothers' wrath. Someguy1221 (talk) 04:23, 11 February 2012 (UTC)

I'm suspicious that common pets have undergone some degree of adaptation as brood parasites. Wnt (talk) 07:52, 11 February 2012 (UTC)

Maybe it's to try and prevent us from destroying the next generation's breeding stock, and ensure sustainability? --TammyMoet (talk) 09:20, 11 February 2012 (UTC)

There's likely several things going on. First off, the "find babies cute so you take care of them" is something that would be evolutionarily necessary for more animals than just humans. In general, it's something all mammals would need (with their reproductive strategy of investing a large amount of effort into a few offspring), so it makes sense that the "find babies cute" would have evolved early and be shared by all mammals. (Most of the "cute baby animals" are mammals - baby flies, baby bees and even most baby birds are ugly as sin, at least from a human perspective. Mitch's baby kangaroo doesn't count because the adults don't see it at that stage. Human embryos in the womb aren't all that cute either.) So the answer to the question "why are most baby mammals cute?" may be much the same as "why do most mammals have hair?" - an early mammal evolved to have cute babies, and the cuteness stuck around because it was useful for many species. The other thing to remember is that it's not so much that babies evolved to be cute, but that "cute" evolved to fit what babies looked like. The large-in-relationship-to-head eyes, the rounded features, etc. are really traits that the babies would have regardless (and are shared by more than just human babies). The innate response to those distinguishing features is primarily there in humans to get us to protect and care for human babies, but there isn't enough harm in finding baby pigs (or baby tigers) cute that humans would evolve to refine our "cuteness" detection to distinguish a big-eyed snub-nosed pig from a big-eyed snub-nosed human. -- 67.40.215.173 (talk) 00:24, 12 February 2012 (UTC)

I found some books and articles ([6]) that discuss how neoteny is accelerated in domestic animals like pets for the reason Wnt says above. But that dosen't completely explain why wild animals would be seen that way. Truthfully it's probably not so much that big foreheads, eyes, and ears are cute so much as those features signify infancy across most mammals and infancy is cute to all of us for obvious evolutionary reasons. Shadowjams (talk) 18:00, 12 February 2012 (UTC)

Another possibility is that we are attracted to young animals since they aren't generally dangerous, and are more trainable, so we have a chance of adopting them and forming a symbiotic relationship. While trying to adopt an adult wolf would have been rather dangerous, attempting to adopt a wolf pup was more likely to succeed (and if it didn't, you'd just kill it and eat it when it got too big). This was no doubt important to human survival, not just for dogs, cats, and horses, but also herd animals, chickens, birds used for hunting, etc. StuRat (talk) 18:45, 12 February 2012 (UTC)

Magnetic liquid

Are there any magnetic liquids? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 03:27, 11 February 2012 (UTC)

There certainly are liquids which would be attracted by a magnet (just mix some oil with iron filings). But a liquid that acts as a magnet sounds difficult to achieve, because the north poles and south poles would bind to each other and cancel each other out. At best, I'd expect one that acts like a magnet when exposed to a magnetic or electric field or charge. StuRat (talk) 03:33, 11 February 2012 (UTC)

We have articles on Ferrofluid and Magnetic ionic liquid. -- 182.232.144.48 (talk) 03:57, 11 February 2012 (UTC)

Stefan–Boltzmann law

I was able to do question i asked above due to the ratio between the stars but i don't know how it actually works. Is the energy the star radiate the same as luminosity?Let use our sun as an example. :$j^{\star} = \sigma T^{4}.$ Ok the sun Temperature is 5778K so according to the formula i do 5778^4 X σ (which is about $5.670 400 \times 10^{-8}$ right?) = $j^{\star}$

$P= A j^{\star} = A \varepsilon\sigma T^{4}.$ Then according to this formula i take the $j^{\star}$ X A (the surface area of the sun). So what number A so that i can put it in my calculator? What unit is A? Like is it in km^2 or m^2 or... The answer suppose to be ~98 lm/W efficacy, that's the luminosity of the Sun. And what is 98 lm/W even mean? I understand apparent magnitude and absolute magnitude but i don't understand this luminosity.

And some other questions i want to be clear. Is the energy the star radiates the same as luminosity? This luminosity is different from apparent magnitude and absolute magnitude.Pendragon5 (talk) 05:24, 11 February 2012 (UTC)

And i want to ask about the units of the constant too: $\mathrm{J\, s^{-1}m^{-2}K^{-4}}$. Is K ^{− 4} supposes to mean that when i use something that has a unit K then the constant = $5.670 400 \times 10^{-12}$ instead $5.670 400 \times 10^{-8}$ right?Pendragon5 (talk) 22:42, 11 February 2012 (UTC)

No, it has nothing to do with that. It means that part of the units of the constant is kelvins-to-the-minus-fourth-power. So when you multiply it by T⁴, which has units of kelvins-to-the-fourth-power, that part of the units cancels out. There may be some information at dimensional analysis, although I haven't read that article (at least recently) so I can't guarantee it. --Trovatore (talk) 09:02, 12 February 2012 (UTC)

Some isotopes of superheavy elements

Has ²⁶⁹Sg been confirmed? What about ²⁶⁶Rf and ²⁶⁸Rf? What values should we use for the atomic weights for rutherfordium ([266] or [267]) and seaborgium ([269] or [271])? Double sharp (talk) 05:57, 11 February 2012 (UTC)

Effect of exercise on metabolism

Must... change... metabolism!

Take a hypothetical individual with a white collar job who is largely immobile, and consequently out of shape. This individual begins to exercise, and burns 300-400 calories per day. However, for each calorie burned, s/he makes up for it by eating exactly as many calories (plus a few extra to balance for digestion).

Which of the following is more likely to be true?

• The individual now has an increased metabolism (the body burns more calories to allow the individual to be ready to exercise at any moment's notice). As such, this person will lose weight in the longrun.
• The individual now has a decreased metabolism (the body has become more efficient at burning calories). As such, this person will gain weight in the longrun.

Magog the Ogre (talk) 08:12, 11 February 2012 (UTC)

Have you read Excess post-exercise oxygen consumption? Exercise will lead to an increase in muscle mass and brown adipose tissue, which both have a higher fuel requirement than white adipose tissue, therefore the increase in basal metabolic rate that occurs after exercise will need to be fuelled by lipolysis. The net effect will probably be weight loss unless you gain sufficient muscle mass to compensate. --Mark PEA (talk) 13:55, 11 February 2012 (UTC)

But, of course, there's no reason to think that this is exempt from the effect of resulting in more hunger, and thus more calories consumed, just like those calories burnt during exercise. StuRat (talk) 18:37, 11 February 2012 (UTC)

Exercise will result in an increase in muscle mass, and increased muscle mass results in increased basal metabolic rate. So yes, the individual will be losing _fat_ in the long run. S/he will probably be gaining muscle faster than he is losing fat under these conditions. Both fat loss and muscle gain will most likely be minuscule (although this depends on the type of exercise.)

However, the assumption that "s/he makes up for it by eating exactly as many calories" is most likely unwarranted - unless the person is under strict supervision, eating pre-portioned and pre-measured meals, and never leaving food on the plate. If you want to ask a more realistic question, ask what happens when that person starts exercising without changing dietary habits (but also without strict enforcement of zero net caloric balance.) In that situation, this individual's appetite most likely will not compensate completely for extra calories burned while exercising. The individual will lose fat, gain muscle, and lose some weight (though not nearly as much as he'd lose if he were to undertake a caloric restriction in addition to exercise.)

According to this 1997 meta-analysis, overweight adults on aerobic exercise programs without caloric restriction end up losing 0.5 lb of fat per week and gaining 0.05 lb of muscle per week, on average. --Itinerant1 (talk) 07:35, 12 February 2012 (UTC)

Many studies go further, and say that not only this individual's appetite will not completely compensate for extra calories burned, but that in sufficiently overweight individuals (but not in lean individuals), the degree of compensation is essentially zero: aerobic exercise does not result in more hunger or in increased caloric intake. [7][8][9][10] --Itinerant1 (talk) 08:26, 12 February 2012 (UTC)

Owl faces

On a slightly related note to (and inspired by) the baby animals thread above...

Has anyone else here heard the theory that humans tend to have very strong visceral reactions to owls (especially unexpected owls), either positive or negative, because the facial proportions of an owl tend to be very close to the facial proportions of a human? Any thoughts on whether this is valid or not? --Kurt Shaped Box (talk) 13:07, 11 February 2012 (UTC)

I have heard it somewhere, but only in a romantic/fantasy novel. In a more practical sense, some owls are quite big - 600 mm or more tall. That's big enough to do some very serious damage if it attacks you, so a fright response to suddenly noticing such an owl close up would be appropriate. Keit143.238.215.185 (talk) 16:11, 11 February 2012 (UTC)

I think we have strong visceral reactions to them because they have huge eyes that are fixed in their faces. Eye contact is a very strong emotional cue. Looie496 (talk) 19:26, 11 February 2012 (UTC)

There's something about their eyes, for certain. When watching videos on YouTube, I can go from thinking that a certain owl is cute, to feeling unnerved on some odd, very deep level, just by seeing it narrow its eyes, or close one eye while leaving the other open, or do a feather trick to change the apparent shape of the head while keeping the eyes fixed. Some sort of uncanny valley thing? --Kurt Shaped Box (talk) 22:02, 11 February 2012 (UTC)

There's a lot of lore connecting owls with alleged extraterrestrial aliens - see Communion (book) and [11]. -- Jack of Oz ^{[your turn]} 03:32, 12 February 2012 (UTC)

I can believe that. Once I was driving down Mount Baw Baw in lightly falling snow when I encountered five Tawny frogmouths sitting on top of five consecutive white roadside posts. With their spread out lower feathers there was a continuity of line from the tops of their heads to the ground. Very alien. Very spooky. (Mentioned that location especially for the Aussies here) HiLo48 (talk) 04:18, 12 February 2012 (UTC)

Squint. It's a Grey alien. --Kurt Shaped Box (talk) 05:58, 12 February 2012 (UTC)

Hysteresis loss in ferrittes

Is it true that the hysteresis loss in a heavily saturated ferrite core will be much less than in its unsaturated state? Will the loss essentially approach zero?--92.28.73.60 (talk) 14:43, 11 February 2012 (UTC)

No - sort of. As coil current is increased from zero, a greater range of magenetisation is tranversed (the area within the B-H loop is increased), therefore the power dissipation increases. If coil current is increased so as to go beyond saturation, the area within the loop cannot increase, and the power dissipated cannot increase beyond a maximum value. The dissipation cannot go to zero as the area within the loop does not decrease. However there is theoretically a complicating factor. The dissipation will increase the temperature of the core. If the curie temperature is approached, the saturation flux density will decrease (essentially, at the currie temperature, typically around 200 C for a ferrite, magnetic materials loose their magnetic properties). This will reduce, but definitely not bring to zero, the hystereis loss in a sort of temperature-saturation feedback loop. You may have been thinking of the Q-factor. The Q-factor of an inductor can increase at currents beyond saturation, as the fraction of back-emf voltage due to the core (with pegged core loss) becomes lower compared to the back-emf due to the intrinsic inductance (the inductance the coil would have with no core at all). A competent designer would never operate a core that way however. To approach the curie temperature in typical cores, you would need very odd operating conditions, such as an ambient temperature likely to give lots of problems. Keit143.238.215.185 (talk) 15:53, 11 February 2012 (UTC)

I should clarify. I meant the loss round a minor loop (due to a small superimposed signal) cf the biasing in the saturation zone. my thinking is that the loss that the small signal experiences should be small.--92.28.73.60 (talk) 16:22, 11 February 2012 (UTC)

Yes - that would be correct. If the core has a very "square" B-H characteristic, the drop in dissipation when the bias current is on would be dramatic, and dissipation could easily be driven to near zero. Keit143.238.215.185 (talk) 16:39, 11 February 2012 (UTC)

Testing medicine by ignorant tested person

To avoid any placebo effect, could a medicine be tested without the knowledge of the tested person? Just imagine that you mix up Prozac in someone's food. Does this, ignoring all legal and moral implication, make sense? Ib30 (talk) 16:55, 11 February 2012 (UTC)

See informed consent. --Tango (talk) 16:58, 11 February 2012 (UTC)

As Tango has said there's little chance that such experiments would get ethical approval. In other words, it doesn't make sense to ignore all legal and moral implications. In any case, it's not clear why it's so important to 'avoid any placebo effect'. A properly designed randomised, placebo controlled, double blind trial is pretty much the gold standard for clinical trials and is generally held to work well. The fact you have a placebo effect isn't considered a show stopper if you account for it. In fact, if your drug has an effect but it's barely as strong as the placebo effect (so potentially could be missed in such a trial), it's unlikely to be considered useful. So there's little point avoiding the placebo effect. (Note a trial without a control group is usually a poor trial. In other words even in this 'secret testing' scenario, you still need a group you aren't giving the drug to, if you didn't realise that you may want to read a bit more about how reserch is conducted.) Also some medicines are not tested against placebos but against existing medicines which you're hoping to beat, or at least match (if the other one is also still patented so you feel you can make money by providing an equally effective competitior). Not to mention if it's secret testing, this is going to make obtaining feedback from the patient difficult. P.S. A number of the links may be useful. They discuss some of the issues with the way clinical trials are conducted. Just as a note I'm not trying to suggest that current practice is definitely perfect, simply that I don't believe you will find many people wishing 'if only we could give our drug secretly to avoid the placebo effect'. Nil Einne (talk) 17:09, 11 February 2012 (UTC)

(Also, merely matching effectiveness might be far from useless with say fewer, milder and/or different side effects, widening a narrow toxic:effective dose ratio, or if enough people are alleric to the first drug) Sagittarian Milky Way (talk) 19:56, 11 February 2012 (UTC)

Note that testing by pharmaceutical companies without informed consent is allegedly quite rampant in Africa. There is very little that can be done at the judicial level about this, on account of the limited scope of most US criminal laws with respects to things that happen extraterritorially, and the secrecy that prevails over such tests. It's not a pretty situation. --Mr.98 (talk) 18:25, 11 February 2012 (UTC)

We actually have a Medical experimentation in Africa although it isn't a great article and seems to be primarily concentrated on historic stuff (perhaps because that's the best documented). I do believe even if companies wanted to, carrying out that sort of stuff even in Africa isn't that likely. It's one thing to give illiterate people information in a language they don't even understand or give children or patients drugs without properly explaining to them or their parents that they are untested and unapproved or misleading about the availability of other drugs; it's another to give them drugs completely secretly since in that case it's fairly difficult to even pretend you have informed consent without outright lying. (I don't think Mr.98 intended to suggest this is likely, I just felt it worth pointing out for the benefit of the OP.) This is not to underestimate the highly dubious practices some companies have shown. While not relating to drug trials, Contaminated haemophilia blood products seems to be another example which I found in this [12] likely somewhat biased source and [13] also has some discussion. Nil Einne (talk) 21:40, 11 February 2012 (UTC)

I've heard various, conflicting reports on it. There are some pretty shady practices going on at the moment. I'm not sure the full extent is known. I'm not sure there's any line between not telling people at all and telling them lies and/or things in a language or jargon they don't understand. --Mr.98 (talk) 01:19, 12 February 2012 (UTC)

So, sometimes lack of moral considerations is good for science? Ib30 (talk) 21:22, 11 February 2012 (UTC)

As well as the problems Nil Einne mentions, drugs trials require very carefully controlled doses. Mashing Prozac into food carries the risk that a) they won't finish their meal (and thus will underdose) or b) they'll take seconds (and will overdose). You'd also run into the problem that if it turns out the drug has an unexpected dangerous side-effect, the people involved in the trial aren't going to report it (which would instantly stop the trial). There's similarly a risk that people will take another drug with it - for instance, painkillers or alcohol or, in the worst case, other prescription drugs. This will a) invalidate the results you get (since you can't separate the effects of the different drugs, and some drugs can cancel each other out or react in unexpected ways) and b) potentially kill the patient. Overall, it wouldn't be recommended. Smurrayinchester 20:03, 11 February 2012 (UTC)

The phrase "good for science" in this loaded question is too vague for a "yes" or "no" answer. Unit 731 in Japan performed all sorts of butchery on prisoners of war without regard for moral considerations, leading (according to our article) to a couple of biological weapons. Was this "good for science"? There was some advance in knowledge, but deciding whether this was "good for science" means you have to weigh this against the costs. Comet Tuttle (talk) 00:35, 12 February 2012 (UTC)

Was the Tuskegee syphilis experiment good for science? Maybe it advanced knowledge of syphilis a tiny bit, but it did so at the cost of human lives and scientific trust. In the long run, such things are not good for science. Scientists are clever — they shouldn't have to resort to unethical practices to learn things. To do so is to be not much better than the Nazis doctors who experimented on their prisoners. That sort of thing hurts science as an institution in the long run in a way that is more profound than the short term gains in terms of data. --Mr.98 (talk) 01:19, 12 February 2012 (UTC)

Nazi human experimentation#Modern ethical issues, though rather short, mentions some interesting issues. It could certainly be expanded, possibly into a page of its own. -- ToE 03:42, 12 February 2012 (UTC)

I can't help but feel that we're part of either a psychological study or possibly a student's essay assignment that hasn't been fully explained to us, but no matter. The phrase "good for science" is, as Comet Tuttle notes, vague to the point of uselessness; it depends far too much on how one chooses to define "good" and "science". One can get into very murky waters very quickly. Consider the testing of a new AIDS/HIV vaccine. What's the 'best' way to determine whether or not it works in humans?

The fastest way to get the answer is to administer the vaccine to a trial group of twenty people, expose those twenty people to live HIV, and then check back in six months or a year to see which ones have a measurable load of HIV in their blood.

How is the vaccine testing actually done? You give your trial vaccine to hundreds or thousands of individuals (generally individuals in higher-risk communities, whom you expect will be exposed to HIV: sex workers, people in countries where there are high overall infection rates, individuals with limited access to barrier products like condoms, etc.); you'll probably also have to give a placebo to the same number of individuals, as the idea of being potentially vaccinated may affect the study participants' behavior and you'll need to control for that. You then wait several years and count the number of HIV-infected individuals in the control group versus the vaccinated group; if there's a statistically-significant difference then your vaccine probably works. Dozens or hundreds of study participants are infected with HIV during the course of the trial, and millions worldwide are infected while waiting for a vaccine.

The first method gives a clearer answer, works faster, and exposes a much smaller number of people to the risk of infection—but would never be permitted. Your assignment is to read the articles on utilitarianism, medical ethics, and devil's advocate, and report back in the morning. TenOfAllTrades(talk) 17:27, 12 February 2012 (UTC)

I don't think anything can be "good for science" or "bad for science" in that way. Science is a method. It isn't a goal. The goal of medicine is to allow people to live longer lives with less suffering. Would human experimentation with informed consent help achieve that goal? Plenty of scientists have asked that question (and not just the war criminals - legitimate, law abiding researchers debate this issue all the time, this is the first paper Google found me on the subject, but there are many others). --Tango (talk) 17:42, 12 February 2012 (UTC)

Brain transplant

Is it at any level possible? a way to transfer one's consciousness (whatever that is supposed to mean) to another body? it can have many good results, such as a cure for sexual identity disorder and stuff like that so... is it possible? Are people even working on it?--Irrational number (talk) 19:07, 11 February 2012 (UTC)

It's a long way off. Also, since your brain is the essential "you", I'd call it a body transplant. StuRat (talk) 19:20, 11 February 2012 (UTC)

No, it's not currently possible. Currently the state of the art is that the brains of a few animals such as frogs can be removed from the body and kept alive for a short while, but they can't be inserted into a new body: the tissue would be rejected, and the spinal cord and other nerves won't make functional connections with the nerves in the body. There is going to have to be a lot of progress before anything like this becomes feasible -- curing spinal paralysis should be very easy in comparison. Looie496 (talk) 19:23, 11 February 2012 (UTC)

I know it's not currently possible, I meant theoretically.--Irrational number (talk) 19:42, 11 February 2012 (UTC)

Head transplant is as close as anyone's gotten. Someguy1221 (talk) 20:21, 11 February 2012 (UTC)

We have an article, brain transplant. The links at the bottom include the related mind uploading article. Comet Tuttle (talk) 21:50, 11 February 2012 (UTC)

Race, gender, testing, intelligence, ability, and predisposition by distraction

I recently listened to http://www.radiolab.org/blogs/radiolab-blog/2009/jan/27/the-obama-effect-perhaps/ which seems to explain quite a bit about several age-old controversies. Does anyone know where to find the peer reviewed research described at 6:30-7:45 and 8:30-8:45 in the recording? Thank you. 85.230.127.113 (talk) 21:47, 11 February 2012 (UTC)

Absolute temperature ?

What is the absolute temperature of the sun? I know its effective temperature is 5778K. In the sun article: it says: "Temperature Center (modeled): ~1.57×107 K"----> is this the absolute temperature of the sun? Or is the Corona: ~5×106 K temperature is the absolute temperature?Pendragon5 (talk) 22:39, 11 February 2012 (UTC)

The suns temperature varies depending on the rasdil distance from its center. I believe its cooler inside.--92.28.73.60 (talk) 22:48, 11 February 2012 (UTC)

Nah it's hotter inside. The deeper you go inside the hotter. I know the sun's temperature varies depend on where in the sun but there is a certain number that stands for absolute temperature. When people talk about absolute temperature of the sun, what is it?Pendragon5 (talk) 23:03, 11 February 2012 (UTC)

The term absolute temperature just means temperature measured on a scale whose zero is absolute zero, for example the Kelvin scale. At the temperatures we're talking about here, it doesn't make a whole lot of difference whether you report the temperature in kelvins or in degrees Celsius. According to our solar core article, the temperature at the center is around 15 million kelvins. --Trovatore (talk) 23:17, 11 February 2012 (UTC)

(On the side issue: The solar corona is indeed hotter than the (somewhat ill-defined) "surface of the Sun". Our article says that the corona is on the order of a million degrees. However this is somewhat misleading because the corona is a very thin gas; your spaceship is safer in the corona than it is at the solar surface.) --Trovatore (talk) 23:25, 11 February 2012 (UTC)

In the Stefan–Boltzmann law article, they says T = absolute temperature. What absolute temperature they are talking about? Let use the sun as an example, there are 3 kinds of temperature: the surface's temperature, the core's temperature and the corona's temperature, so which is the one they are using in the formula?Pendragon5 (talk) 23:38, 11 February 2012 (UTC)

In that context, T is the absolute temperature of the radiating object, whatever it happens to be. For the case of the Sun, you want to use the temperature at the "surface of the Sun" (a slightly ill-defined notion as I mentioned). Of course, the other parts of the Sun are also radiating, but the parts below the surface radiate light that gets quickly re-absorbed (so we never see it), and the parts above the surface are too thin to contribute much. --Trovatore (talk) 23:57, 11 February 2012 (UTC)

You may find the article photosphere useful. It discusses what effective temperature really means in this context and how it relates to the actual temperature of the star at various depths. (Note, T is the Stefan-Boltzmann law is the effective temperature - when it says "absolute" it just means it is measured relative to absolute zero, it doesn't mean that it's the actual temperature of the star.) --Tango (talk) 17:49, 12 February 2012 (UTC)

light speed limit

Im no expert but when you say that you'll go back in time if you travel faster than light the same thing as saying that only superman can run for 500mph. MahAdik _usap 23:18, 11 February 2012 (UTC)

I sort of see what you're saying. The way I heard it explained is that we are travelling through time at the speed of light. If you travel in our three dimensions, you are either adding to or taking away from the speed we travel in time. So if you can go faster than the speed of light, then time is travelable. Does this help? --T H F S W (T · C · E) 23:35, 11 February 2012 (UTC)

(edit conflict) I'm having trouble finding the question here. But if you're asking if it is impossible to travel faster than light, and thus not possible to go back in time, then yes, more or less that's the case. If you could travel faster than light, there would be reference frames in which you could be perceived as traveling back in time. It's a complicated thing. See Tachyonic antitelephone for something of an explanation, though I don't know if it will be comprehensible unless you've got a little more science under your belt... --Mr.98 (talk) 23:38, 11 February 2012 (UTC)

If this helps, the reason that you can't travel as fast as light is that it would take an infinite amount of energy to get you up to that speed, as discussed at our article section Speed of light#Upper limit on speeds. Comet Tuttle (talk) 00:17, 12 February 2012 (UTC)

I asked because i think that all the fuzz about the possibilty of time travel is just a misunderstanding about the light speed limit, But of course i can be totally wrong. MahAdik _usap 00:20, 12 February 2012 (UTC)

You will probably enjoy our article Time travel. Comet Tuttle (talk) 00:24, 12 February 2012 (UTC)

I really liked the answer given by T H F S W. Its just the same as I believe (and of course its true). I think its called the Minowski invariant or something.--92.28.73.60 (talk) 01:19, 12 February 2012 (UTC)

Except that you cant add to the speed we travel through time: you can only subtract from it. :-( — Preceding unsigned comment added by 92.28.73.60 (talk) 01:35, 12 February 2012 (UTC)

February 12

Dihydrotestosterone

Does an adult need Dihydrotestosterone? What will happen if he won't have it? — Preceding unsigned comment added by 87.68.222.18 (talk) 00:13, 12 February 2012 (UTC)

Does our article Dihydrotestosterone answer your questions? Comet Tuttle (talk) 00:21, 12 February 2012 (UTC)

The distance of the hair matrix to the scalp

Hi,

I would like to know, what is the distance of the hair matrix to the scalp, in an averge adult person. — Preceding unsigned comment added by 87.68.222.18 (talk) 00:15, 12 February 2012 (UTC)

Not an answer, but a note that our article Matrix (hair) is a tiny stub despite the enormous category template it's got. Comet Tuttle (talk) 00:36, 12 February 2012 (UTC)

Alkali metals

Who first suggested the name "alkali metal" for the group 1 elements? What was the etymology of the name? Double sharp (talk) 03:24, 12 February 2012 (UTC)

The word alkali comes from the Arabic word meaning "ash", see [14]. Some of the earliest common compounds featuring alkali metals were things like soda ash and potash, which are sources of sodium and potassium respectively, and which provide the names for both of those items. Today, alkali means the same as "basic", in the "acids and bases" sense, and alkali metals will, after reacting with water, produce solutions of very high pH (bases) like sodium hydroxide and potassium hydroxide. I'm uncertain who specifically came up with the name; but a good guess would be Humphrey Davy, who is credited with being the first chemist to isolate many metals, including the alkali metals. --Jayron32 03:57, 12 February 2012 (UTC)

Almond appleseeds

Why do apple seeds smell like almonds? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 04:37, 12 February 2012 (UTC)

Because they contain hydrogen cyanide. --Jayron32 04:39, 12 February 2012 (UTC)

Then would not the smell of appleseeds contain a sufficient level of hydrogen cyanide to be lethal? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 04:42, 12 February 2012 (UTC)

No, the ability of one's nose to detect trace amounts of HCN is significantly lower than toxic amounts. HCN is certainly very poisonous, but the amount one gets from appleseeds is trivial. It doesn't occur in the seeds directly, but rather it "outgasses" from them due to the slow decomposition of organic cyanide compounds. Lots of fruits seeds and pits, including almonds themselves, will release very small, trace amounts of HCN. You'll notice that people aren't dropping dead from eating cherries or apples, so empirically we know it mustn't be a problem. --Jayron32 04:51, 12 February 2012 (UTC)

People do not typically eat appleseeds. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 04:56, 12 February 2012 (UTC)

No, but even if they did they are harmless. --Jayron32 04:58, 12 February 2012 (UTC)

You guys must have different apples. When I was at primary school, we were taught not to eat apple seeds, and I'm sure I've read that eating one or a few on rare occaisons won't hurt you, but routinely or often eating them will. The cyanide present in the seeds does not get into the apple flesh. Keit121.221.97.9 (talk) 05:38, 12 February 2012 (UTC)

Snopes says "the body can detoxify cyanide in small doses, and the number of apple seeds it takes to pack a lethal punch is therefore huge". The BBC gives the lethal dose as 30,000 seeds. So pip, pip, cheerio. Clarityfiend (talk) 09:36, 12 February 2012 (UTC)

By the way, the Snopes article gets a couple of things wrong. It says that cyanide kills by preventing the blood from carrying oxygen. Close but not quite — it does bind to hemoglobin, but the actual deadly effect comes from its binding to cytochrome oxidase a, inside the cells using the oxygen. And there is a recognized antidote, sodium thiosulfate if I remember correctly, although it doesn't always work. --Trovatore (talk) 10:37, 12 February 2012 (UTC)

Our article on cyanide poisoning has a pretty thorough overview of therapeutic options. TenOfAllTrades(talk) 16:20, 12 February 2012 (UTC)

I vaguely remember reading somewhere that "one man died from eating as little as a cup" of apple seeds. (Or was it an eighth of a cup? I think it must have been a cup, because an eighth of a cup is an ounce, and they'd have said that instead).

Anyway, I thought it was amazing that anyone would have the patience to gather together a cup of the things to eat them, but that's probably a lot fewer than 30,000.

Personally, when I eat an apple (which is rarely — not my favorite fruit at all), I usually peel and chew one or two of the seeds for the pleasant almond flavor. Hasn't killed me yet. --Trovatore (talk) 09:56, 12 February 2012 (UTC)

A little pedantic, but an eighth of a cup is a fluid ounce, not an ounce. The mass will depend on what it is an eighth of a cup of. --Tango (talk) 18:00, 12 February 2012 (UTC)

Formula question

And in Luminosity article, in the astronomy section. They says "In measuring star brightnesses, visible luminosity (not total luminosity at all wave lengths), apparent magnitude (visible brightness), and distance are interrelated parameters. If you know two, you can determine the third." What exactly the formula they are talking about? Is visible luminosity in this case they actually meant absolute magnitude? Thanks!Pendragon5 (talk) 06:16, 12 February 2012 (UTC)

Two versions of the formula are given at the end of the first subsection of the "In astronomy" section. The simplest is m_star = - 2.72 - 2.5 · log₁₀(L_star/dist_star²), where L_star is in terms of solar luminosities, and dist_star is in light-years. Since absolute magnitude is the apparent magnitude a star would have if it were 32.6 light-years (10 parsecs) away, it can be obtained from visible luminosity by plugging 32.6 light-years for dist_star in the formula. Doing this should simplify to M_star = 4.83 - 2.5 · log₁₀(L_star) where 4.83 is the absolute magnitude of the Sun. 98.248.42.252 (talk) 16:22, 12 February 2012 (UTC)

Novim

What does Novim do? Why do they say they are for science without advocacy? How is that different from awareness without action? Meow Will Always Love You (talk) 09:20, 12 February 2012 (UTC)

T Tauri

Why in the observation data of the this article, there are so many question mark? Many info about this star is not in the observation data. Is it because we don't know them yet or we haven't update it? So if possible can someone update the date please. It is maybe outdated.Pendragon5 (talk) 09:21, 12 February 2012 (UTC)

I'm a little confused as to how you think the question marks can be changed to values as the article says it's a triple star system, and the question marks refer to single stars only. I'm not familiar with the way Wikipedia handles triple star systems though. --TammyMoet (talk) 14:31, 12 February 2012 (UTC)

Actually it's binary star system. And i don't know if it's possible to have values of the ? marks.Pendragon5 (talk) 19:10, 12 February 2012 (UTC)

The article says "The T Tauri system consists of at least three stars" so if the article is wrong, correct it if you have sources to back your statement up. Maybe those sources will also give values for you. --TammyMoet (talk) 19:50, 12 February 2012 (UTC)

Mice

Are there any major physical or behavioral differences between lab mice and wild mice? Would a lab mouse put into a litter of wild mice babies grow up as a wild mouse? Could a wild mouse be kept as a pet and learn to be handled the way lab mice can? Would a wild mouse run in a wheel? Boredtolife (talk) 15:31, 12 February 2012 (UTC)

As far as I know lab mice are not domesticated to the same extent that say cows and sheep are. So yes, a lab mouse let into the wild would become Feral. For a wild mouse (if raised from a pup) in captivity with lots of human handling, it would be susceptible to Imprinting – thereby appearing tame. A captive wild mouse in a small cage (raised from a pup -so it was not afraid to be observed), would still want the stimulation of running in a wheel if one was to be made available. In very large Vivariums, the attraction of wheels fades, as there is plenty of space to run around in. The Homo sapien show something similar to 'wheel behaviour' when forced to live in cities. They spend an awful lot of time hammering away at a keyboards, to get stimulation from something they refer to as the world wide net. This behaviour makes lab mice seem almost human.--Aspro (talk) 19:31, 12 February 2012 (UTC)

A closer comparison might be people who ride on a stationary bicycle or use a tread mill. StuRat (talk) 19:40, 12 February 2012 (UTC)

As for physical differences, lab mice are often bred to be white, presumably so they are easier to see, and to differentiate an escaped lab mouse from a wild mouse that happens to get into the lab. Different breeds of lab mice also are bred with specific genetic problems, to aid in studying humans with the same problem. For example, diabetic mice might be bred. StuRat (talk) 19:39, 12 February 2012 (UTC)

how does the body metabolise alkenes and alkanes?

These are different from regular fatty acids. I'm wondering if the same mechanism is used to metabolise trans fats. Do bacteria eventually metabolise it? Are alkenes and alkanes taken into the bloodstream? If so, how are they excreted? 216.197.66.61 (talk) 17:58, 12 February 2012 (UTC)

My guess is that alkanes probably pass through the body without anything interesting going on - though n-hexane has known toxic effects so something must be going on there. I'd also suspect that alkenes get converted to alcohols in the strong acid of the stomach via Hydration reactions. LukeSurl ^{t c} 19:06, 12 February 2012 (UTC)

Symbol?

$\frac{L}{L_{\odot}} \sim {\left ( \frac{M}{M_{\odot}} \right )}^{3.9}$ What is the ~ mean in this case? This is a formula taken in luminosity article.Pendragon5 (talk) 19:09, 12 February 2012 (UTC)

data interpretation

Let use Proxima Centauri as an example. In the data, section "observation data" and "characteristics". Each of them has an apparent magnitude. What is the difference between them? What is the actually apparent magnitude of that star?Pendragon5 (talk) 19:45, 12 February 2012 (UTC)