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July 20

Pre-CPR resuscitation

Early- and mid-20th century films sometimes depict a pre-CPR method of resuscitation, in which the body is laid on the back, the arms put at the side, and then moved behind the head before being returned to the side; this is repeated until the person breathes or (thought this isn't often shown in the films) until the resuscitator gives up on the hopeless case. What do we call this method? Nyttend (talk) 03:06, 20 July 2014 (UTC)

At History_of_cardiopulmonary_resuscitation I see the idea of lifting the arms, but that sounds like "up in the air" not "along the ground to behind head" as you describe. Anything you find, please add a note to that article. DMacks (talk) 03:25, 20 July 2014 (UTC)

There's also a mention at Cardiopulmonary resuscitation#History. HiLo48 (talk) 03:30, 20 July 2014 (UTC)

Yes, I was thinking of the lifting-in-the-air; I wasn't describing moving the arms along the ground. Think vaguely of the motion backstroke swimmers use. Sorry that I missed the history section in the CPR article; I looked for it and somehow completely failed to find it. Nyttend (talk) 04:16, 20 July 2014 (UTC)

That's because this material belongs in the article on artificial respiration, which came before CPR. Or maybe the two articles should be merged. --50.100.189.160 (talk) 04:45, 20 July 2014 (UTC)

I was taught this every time I refreshed my First Aid at Work qualification because it is useful in cases where the patient is believed to have ingested poison per ora or where there is a lot of blood round the oral area and you are worried about oral transmission of disease. --TammyMoet (talk) 08:43, 20 July 2014 (UTC)

It's called the Sylvester method. --173.49.18.131 (talk) 05:03, 21 July 2014 (UTC)

Ca and K sorbates?

what does it mean? [1] --84.108.213.48 (talk) 07:27, 20 July 2014 (UTC)

I think I had understand : Potassium sorbate + Calcium sorbate, but I need to read it again. thanks --84.108.213.48 (talk) 07:31, 20 July 2014 (UTC)

Yes, that's right --50.100.189.160 (talk) 09:49, 20 July 2014 (UTC)

Number of employees at the Russian Federal Space Agency

How many employees does ROSCOSMOS (the Russian Federal Space Agency) have? Thanks. --Schweinchen (talk) 13:47, 20 July 2014 (UTC)

Voltage divider - question about current

Suppose I have a device that draws 1 A at 6 v and I have a 12 v supply so I make a voltage divider with two 1 Mohm resistors. Now I can have 6 v across my device but how could it draw 1 A through that 1 Mohm resistor? This was completely neglected at school (a long time ago). 78.148.105.159 (talk) 15:34, 20 July 2014 (UTC)

it can't. whatsmore, any load except very small ones (several megaohms) will upset the divider because of how parallel resistances add. That's why voltage dividers are never used as sources of voltage (except in transistor stages, to provide bias voltage to the base, but then the base only draws microamps (huge base-emitter resistance), so it's OK). if the device draws 1A at 6V, then you could connect it through a 6 Ohm series resistor, which would drop 6 V and dissipate 6 W (!) of power as heat, but that's also "suboptimal." If the voltage is AC, one could use a simple stepdown transformer. DC requires the use of DC-DC converters, such as the 7806, which is a linear regulator (there are other conversion methods, such as when you have an oscillator generate a square wave with an adjustible duty cycle, then smoothen the voltage out with a capacitor, or by generating a sinusoid which is then power-amplified and fed into a transformer etc) Asmrulz (talk) 17:35, 20 July 2014 (UTC)

The LM7806 regulator is a good suggestion. It will deliver fixed 6V whether a load (up to 1A) is connected or not and it will tolerate a short circuit. But note that when the device takes 1A, the device and the regulator are each dissipating 6 Watts. Therefore the regulator which comes in a TO-220 package should be bolted to a Heat sink. If you know the thermal resistance of the heat sink, say 3 deg C/W, then in this application the regulator runs at 6 x 3 = 18 degrees above ambient temperature, which is reasonable. Read the application note for other information such as the pin connections and the capacitors that should be soldered close to the regulator to ensure stability see Fig 4. 84.209.89.214 (talk) 21:32, 20 July 2014 (UTC)

Don't use a voltage divider as a power supply, because it's inefficient, it's sensitive to imperfections in your (probably non-) ideal voltage source; and even if it works, it loses a lot of energy to resistive heating. Real power supplies that source large currents do not use voltage dividers to set the output voltage. Nimur (talk) 17:37, 20 July 2014 (UTC)

Voltage divider#Loading effect mentions this problem, but I added another mention earlier in the article since it seems rather important. -- BenRG (talk) 17:40, 20 July 2014 (UTC)

Use an op-amp. You can tie it to the 12V rail, tie one input to the divider at 6V and a 6 ohm resistor at the output. Tie the output to the other input. The opamp will drive the load to keep the inputs difference at 0 volts. So you end up with the opamp driving 6V into any load you like. See Voltage follower. --DHeyward (talk) 07:25, 22 July 2014 (UTC)

A linear regulator, or an op amp or any other active semiconductor solution will be more satisfactory than a simple dropping resistor if the demand of the device varies, since the active device can keep the voltage supplied to the device from varying. But a better approach for high current like 1 amp out at 6 volts is a DC to DC power supply which converts the DC to AC and uses a transformer to drop the voltage before converting it back to DC. That can be far more efficient. These DC to DC power supplies have largely replaced the "old school" solution for high current DC voltage conversion which would have been a motor generator set, with a 12 volt motor driving a 6 volt generator. It could be a rotating machine with one shaft and one field winding. Edison (talk) 17:29, 22 July 2014 (UTC)

What do insect bites do to your skin tissues?

Bites by many insects result in rashes, which may last from hours to few weeks. What do insect bites do to your tissues? For the ones that take a few weeks to completely clear up, what makes recovery take soon long? What's happening when your tissues are recovering from an insect bite?

For those which aren't trying to harm you, like a mosquito, it's often a bacterial infection. The mosquito injects a blood thinner so it can avoid clotting while drawing blood, but that's also full of bacteria and viruses. Having microbes injected directly into the blood vessel is one of the worst places for it, since it can't be ejected by bleeding, as in a normal cut, or killed off by free oxygen, in the case of anaerobic bacteria, or removed/killed by washing and sterilizing the wound. At that point, it's up to the immune system to counter the infection.

For those which are trying to harm you, like venomous spiders (not technically insects), the venom may work by any of a number of methods. In any case, first the venom must be diluted to the point where it no longer causes damage, then the damage must be repaired. StuRat (talk) 16:35, 20 July 2014 (UTC)

Even a non-infectious mosquito bite can cause an allergic reaction, which believe it or not is called Skeeter syndrome. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:12, 20 July 2014 (UTC)

Good point. Note that many of the same problems I noted above also apply to an allergen injected directly into a blood vessel, such as the inability of bleeding to wash it away. StuRat (talk) 17:23, 20 July 2014 (UTC)

• Typically there are two types of reaction from blood-sucking flies and mosquitoes. The first and subsequent bites will from a histaminic which will be local swelling, redness and itching due to the response to the direct tissue damage of the bite. If the body forms antibodies to chemicals in the flies' saliva, in later bites, some minutes after the initial red, pimple-like reaction, the skin will become raised and hardened in the shape of a coin or a pancake. This is called induration, and is caused by white blood cells responding to the presence of activated antibodies. Odly we lack an article on induration. μηδείς (talk) 17:36, 20 July 2014 (UTC)

• Beware those bites shaped like a con. They sound dangerous. :-) StuRat (talk) 19:31, 20 July 2014 (UTC)

Unless you're goining to start paying me Stuart, don't expect me to notice things the spelczeck doesn't. μηδείς (talk) 23:01, 20 July 2014 (UTC)

Is a spellCzech an Eastern European wizard ? StuRat (talk) 20:28, 21 July 2014 (UTC)

An Eastern European editor wizard... 24.5.122.13 (talk) 00:06, 22 July 2014 (UTC)

Salt poisoning

Our hypernatremia article mentions salt poisoning as one possible cause. However, we have no article on that. Is salt poisoning simply consuming so much salt in a short time period that your body is unable to compensate by drinking water and urinating salt, in order to bring the sodium balance back to normal ? If so, how much salt intake causes this ? For example, according to this nutrition menu from Chili's, ordering a full order of Texas Cheese Fries as an appetizer followed by a Margarita Shrimp Bowl for the entree and a Molten Chocolate Cake for dessert will result in about 12 grams of sodium: [2]. So, would this cause salt poisoning, if consumed within an hour, by a 200 pound man ? How about a 100 pound woman ? StuRat (talk) 19:28, 20 July 2014 (UTC)

This page has the Center for Disease Control recommendations for sodium intake. At Wikipedia, we cannot diagnose whether or not any action you or someone you know has taken or plans to take would cause a medical problem. Only a doctor would. --Jayron32 19:42, 20 July 2014 (UTC)

That's not particularly helpful, as it deals with chronic excessive sodium intake, and I asked about an acute overdose. And I believe you can state whether a particular level of sodium intake would cause medical problems in a theoretical individual. For example, is there an LD50 value for sodium ? StuRat (talk) 21:25, 20 July 2014 (UTC)

See here section 11. --Jayron32 04:00, 21 July 2014 (UTC)

Let's see, that lists the LD50 as 3-10g per kg of body weight, and a 200 pound man is around 80kg, so that means it would take 240-800 grams to reach the LD50 for him, and 120-400 grams for the 100 pound woman. That's a lot more than I thought. Also, what is the minimal acute lethal dose ? StuRat (talk) 16:04, 21 July 2014 (UTC)

I'm also interested in knowing what the minimum sodium intake is. I believe the 1.5-2.3 grams stated in the previous link is the range for maximums. StuRat (talk) 21:29, 20 July 2014 (UTC)

It varies. This page notes that only about 180 mg per day are needed for a person who doesn't sweat (that's 0.180 grams), but recommends a minimum of 1500 mg (1.5 grams) for a healthy adult. this page is a bit older, and recommends a safe minimum of 500 mg per day. --Jayron32 04:00, 21 July 2014 (UTC)

From here [3], it indicates that risk as a function of salt intake appears to follow a "J" shaped curve, they also mention that less than 3g per day is associated with risk - they mention that the current guidelines are from projections based on small samples and short term trials; so there does appear to be some controversy. This [4] appears to indicate that low sodium diets can raise various other levels, not all good; the general conclusion being that low sodium diets aren't necessarily beneficial to those without high blood pressure - though, there main recommendation is further testing. This [5] mentions that lower sodium excretion is associated with higher CVD mortality. This [6] concludes that the current guidelines are not supported, but that raising sodium intake is also not supported - in short, recommendation either way does not appera to be supported. This [7] indicates that sodium restriction can have risks to cardiovascular health. These, may also be of interest: [8], [9], [10], [11]. In short, it does not appear that it is supported that a sodium restricted diet is necessarily healthier, nor necessarily healthy - this is not to say that a high salt diet is safe either. There is some sweet spot somewhere in there, but the current US recommendations may be on the too low side (even if the average American consumes too high on the high side...), at any rate, the issue is controversial, and I don't think there is any clear answer at present.Phoenixia1177 (talk) 06:05, 21 July 2014 (UTC)

As for the original question, I couldn't find nearly as much info. These are MSDS for Sodium chloride: [12], [13] which mentions oral toxicity (search for "ld50"). This [14] (pdf full article: [15]) discusses salt toxicity and the case of an accidental deat due to salt poisoning in an adult. Here's a news article on someone in jail for not intervening/causing in a case of salt poisoning (involves her child) [16]. This is for animals, but might be relevant: [17]. At any rate, it would appear that it would take a large amount to actually cause acute poisoning - however, the amount and impact on a large dose of salt in a dehydrated individual would be more pronounced. (This [18] also has a bunch of info, search "range of toxicity".)Phoenixia1177 (talk) 06:33, 21 July 2014 (UTC)

Thanks. I never expected dietary sodium recommendations to be so controversial.

I've also wondered if people in food eating contests involving salty items might be in danger of salt poisoning. (At the top level, though, most of the food is quickly vomited back out or passes through undigested, so that would hopefully limit the sodium absorption.) StuRat (talk) 16:05, 21 July 2014 (UTC)

I have no source, but I believe a major inhibiting factor would be the time it takes to digest food. The cases I read about involved children, a mentally handicapped woman eating jam with large amounts of salt added in place of sugar, and people who were given saline enemas. In those cases, the needed dose is either smaller (children) or was from a source that allowed large amounts to be absorbed quickly. For an eating contest, using hot dogs as an example, you'd need to directly absorb the salt content of 60 hot dogs before reaching significant toxic levels (70kg person) - for someone like Takeru Kobayashi, this may be possible, but the digestion time factor should still put him in a safe zone, even if he didn't vomit any of it back up. Finally, it is possible that such people may intake enough to suffer from limited poisoning, but, again, digestion time would most likely prevent this. In almost any situation involving actual food, it is most likely that the eater would vomit before they could take in enough food - and, again, even if not, with digestion time being a factor, it is likely that the person would never have enough salt at anyone time due to excretion. -- Again, I have no direct source, but I would say that this would be almost impossible to do with standard food items under normal circumstance.Phoenixia1177 (talk) 08:24, 22 July 2014 (UTC)

However, some people seem to lack the vomit response. (I wonder what percentage that is.) Fortunately my vomit response is quite good. I've never had a hangover, for example, because consuming enough alcohol to cause one would just make me to vomit it back up. StuRat (talk) 12:21, 22 July 2014 (UTC)

Perhaps, but I imagine very few people lack the vomit response and can fit 60+ hot dogs in their stomach while near dehydration, which is what you would need to even near a risky level through food. On the other hand, if you did lack a vomit response and chugged salt water, or something like it, you might be able to poison yourself, but it certainly would be on purpose or do to weird circumstance and mental handicap. Essentially, if someone gets salt poisoning through ingestion, then it was either purposeful, the result of mental handicap and weird circumstance, or some survival style situation (as in a ship wreck). The only cases I've heard of that may be accidental and involving normal people are in the case of saline enemas; and I'm not sure how common it is that someone receives one, nor what portion of those get poisoned.Phoenixia1177 (talk) 00:46, 23 July 2014 (UTC)

I many movies people are shipwrecked, adrift in a lifeboat, and very thirsty. They are cautioned not to drink seawater, but inevitably someone does and promptly dies in agony after one good drink. If a 100 pound woman would have a LD50 of 129 grams minimum, and seawater is 3.5% salt, (roughly 35 grams salt per liter) then her lethal drink would be about 3.4 liters. The real story likely is that the person who starts with say a 250 ml drink of seawater actually winds up more thirsty as a result and more and more seawater drinking as time passes, and a day later is worse off than the person who didn't drink seawater, and dies sooner than that person, but not instantly. Edison (talk) 17:14, 22 July 2014 (UTC)

Plus they presumably had a high sodium to water ratio in their body to begin with, due to dehydration. StuRat (talk) 00:06, 23 July 2014 (UTC)

How can we know that electrons cannot be broken down into smaller constituent parts

Just tell me how? OsmanRF34 (talk) 20:58, 20 July 2014 (UTC)

We can't know for sure. We can however state that there is no verifiable evidence that they can be. If you want absolute certainty, you won't find it in science... AndyTheGrump (talk) 21:01, 20 July 2014 (UTC)

See preon. Wnt (talk) 21:05, 20 July 2014 (UTC)

In general, as particle accelerators move to higher and higher energies they probe smaller and smaller structures. Broadly speaking, studying interactions with higher and higher energy particles has allowed us to first discover the nucleus of atoms, and then the constituent nucleons, and then the quarks from which nucleons are made. Such tests have not revealed any internal structure to the electron, which either implies it doesn't exist (i.e. no smaller parts) or the constituent parts are so tightly bound that they can't be revealed by the energies we have available to probe for them. Given the lack of evidence for internal structure, it is simpler to assume that no constituent parts exist (e.g. Occam's razor). Dragons flight (talk) 09:36, 21 July 2014 (UTC)

Wouldn't it be more advisable to assume that up to energy level x, there could not be found any particles, but above this, we don't know? That would be the same assumption, but with a reasonable limitation.OsmanRF34 (talk) 10:39, 21 July 2014 (UTC)

That's why I linked Occam's razor. The simpler assumption (i.e. less complicated theory) is that there are no constituent parts. That doesn't make it right, but in the absence of evidence assuming anything else just makes your theories more complicated without explaining anything new. Of course, some people do make theories about what electron constituent parts might look like (e.g. preons) and what consequences they might have, but until there is some experimental evidence for such theories that can't be explained the traditional way, most scientists are just going to assume electrons have no constituent parts. Dragons flight (talk) 17:19, 21 July 2014 (UTC)

What do you want particle physicists to do that they aren't already doing? Obviously they haven't ignored the possibility of preons, as witnessed by the existence of the word "preon" and the papers on the subject. Preons are just one of many possibilities for beyond-the-Standard-Model physics, and without experimental guidance it's not clear how much time one should spend on that possibility and how much on others.

One theoretical argument against preons (which is mentioned in the article) is that they would have to have a much larger mass than an electron in order to be confined in such a small space without violating the uncertainty principle. You might be able to cancel that with a negative binding energy, but it's not clear why the binding energy would be so close to minus the sum of the preon masses. To the extent that physicists disbelieve in preons, I suppose this is why.

Also, the fact that the fundamental Standard Model fermions are all massless and chiral seems to me to rule out their being composite, but professional physicists have proposed preon models post-Standard-Model, so I must be wrong about that. The article does say that the discovery of the Higgs boson ruled out many of the models. -- BenRG (talk) 18:46, 21 July 2014 (UTC)

What is the difference between ECG and Monitor?

What are the main differences between ECG and monitor? מוטיבציה (talk) 21:28, 20 July 2014 (UTC)

An electrocardiogram can be displayed on a monitor and/or recorded on paper tape. The paper tape version traditionally had the advantage of allowing quicker access to recent data which had scrolled off the monitor. However, modern systems both electronically record the data and hopefully allow rapid access to recent data, but it's still hard to get quicker than paper tape. Paper tape does need to be changed periodically, however. In a third world hospital, where power disruptions are frequent, paper tape records may also be more reliable. StuRat (talk) 21:37, 20 July 2014 (UTC)

See also heart monitor. (I'm guessing that's what you mean by "monitor" which is a rather general term.)--Shantavira|^{feed me} 06:04, 21 July 2014 (UTC)

July 21

Time loops

Could time loops actually exist in real life? Clover345 (talk) 00:05, 21 July 2014 (UTC)

Probably not, but existing theory doesn't currently completely rule out that possibility. There do exist solutions to the Einstein field equations which contain closed timelike curves, but those solutions generally require circumstances which have never been observed, and hence may never exist. See also Chronology protection conjecture. Red Act (talk) 01:54, 21 July 2014 (UTC)

See Time loop. The Novikov self-consistency principle is needed to avoid paradoxes, such as the Grandfather paradox, arising if a Closed timelike curve (CTC) existed. Most physicists feel that CTCs are artifacts. 84.209.89.214 (talk) 15:31, 21 July 2014 (UTC)

On the contrary, this assumes a classical (i.e. nonquantum) approach. I recall reading an article in Scientific American many years ago in which a quantum approach resolved this by showing that natural solutions existed, without having to resort to paradox-avoiding principles. My own guess is that this would be easiest understood in the Many worlds interpretation. I would tend to de-emphasize the statement about "Most physicists ..." in this context. —Quondum 18:43, 21 July 2014 (UTC)

The main thing I want to know about a time loop is the entropy of an isolated system within the loop. Either it's a theorem that you can't keep the system isolated (Novikov forbids it) or else the "direction of time" within the loop should reverse to point from the lowest-entropy point to the highest-entropy point, at least within the isolated system. Right??? Wnt (talk) 18:57, 21 July 2014 (UTC)

I disagree – you're coming at it from the perspective of being able to assign an entropy density to a point on the spacetime manifold. However, entropy is essentially specific to each observer, which is essentially connected to a what could be called a history (I don't know the terminology in MWI, so I'm improvising). Thus, an observer can see a different entropy on each circuit, even assuming a GR-like manifold. Remember that an observer does not see the "whole" wavefunction. An observer on each loop sees different histories (pasts).

Disclaimer – I'm headed into speculation here; my point is simply that the converse should not be taken as a given. —Quondum 00:10, 22 July 2014 (UTC)

In fiction I've seen this problem overcome by having a piece of information make the loop, not a physical object. For example, a document is transcribed then sent back in time to become its own source document. This prevents the problem of wear and tear on an "infinitely" old object. Katie R (talk) 19:33, 21 July 2014 (UTC)

da ja vw is a time loop . Thanks water nosfim

Some history questions about the ECG development

Hello everybody, I have some questions about the history of the EKG, and I would like to know the answers. 1. In the book "Dubin: rapid interpretation", written that "Galvany knew that the closing circle between two metals to dead frog's leg, creates an electric current". According to this thing, if someone takes a gold and silver for example (two different metals), his legs dance... but it does not happen in the reality. if so, what is the explanation for the things that mention above? 2. There written too "Koliker and Muller recover that when putting a motor nerve of grog's leg on a beatting heart, then the leg moves according to the beats", it does not clear to me what kind of heart he's talking about, Is it talking about human heart, and how they did that (what is the way they did it to approach to the beatting heart in order to make their research? מוטיבציה (talk) 02:40, 21 July 2014 (UTC)

Rapid Interpretation of EKG's by Dale Dubin is a long-time best-selling textbook.

EKG#History is another place to start reading. EKG or Electrocardiography is the study of natural electric signals in the living body. You have been reading about the much older experiments on reactions of muscles to externally applied electricity that were started by Luigi Galvani. Two different metals placed in contact can produce an electric voltage; some pairs of metals are useful for sensing temperature or for controlling corrosion. Gold+silver together generate very little voltage, too little to demonstrate a galvanic reaction on a person (though I suspect your book's author was joking). However be assured that if one joins sufficiently many Electrochemical cells in a series circuit to get enough (over 100V) potential, it will make anyone's leg "dance involuntarily". Koliker and Muller's work is cited in History of Defribrillation that you can view at the link. 84.209.89.214 (talk) 13:55, 21 July 2014 (UTC)

which is the top,best institute to get trained on "Telecom Protocol Testing" course in india?

am a b.tech e.c.e fresher(2014) without any experience in any field,kindly please suggest the top,best institute to get trained on "Telecom Protocol Testing" course in india?

I would suggest that you finish your electrical engineering degree first. This should include units about communications protocols. An employer will very likely give on the job training on how to use the equipment and facilities they have for testing. Any course you do now will probably be dated by the time you are employed. But on Wikipedia you can read Bit error rate test jitter loopback test, Ping (networking utility), traceroute, Optical time-domain reflectometer all the topics linked from Interference (communication) to get an idea. If you want to go further to prove yorself, you could write a page for Wikipedia on a related topic. Graeme Bartlett (talk) 22:54, 21 July 2014 (UTC)

Importance of Coking Coal

Why is coking coal the only form of carbon useful for steel manufacture? Why can't it be substituted with other carbon sources like graphite or dehydrated sugar [19], etc. 202.155.85.18 (talk) 09:43, 21 July 2014 (UTC)

Coking coal is about $100 / ton. Mineral derived graphite is about $2500 / ton (plant-derived graphite is even more). I don't think it is that one can't ever use other carbon sources, but rather that they choose to use the cheapest carbon source available that is also pure enough that it won't impact the steel too much. Dragons flight (talk) 09:55, 21 July 2014 (UTC)

Coke used to be cheap in the UK too, but it's now four or five times the US price if Dragons flight's estimate is accurate. Perhaps it's because we no longer make town gas here. Sugar is not much more expensive here, but unsuitable in its hydrated form. Dbfirs 20:49, 21 July 2014 (UTC)

For manufacture of low-carbon steel, gas can be used as well... 24.5.122.13 (talk) 00:03, 22 July 2014 (UTC)

High purity carbon is made easily and cheaply from charcoaled coconut husk in equatorial countries. This is used for carbon absorption like in CIL/CIP gold production. I can't imagine that it's more expensive than coking coal. Is there a particular reason why it may be unsuitable? 202.155.85.18 (talk) 00:44, 22 July 2014 (UTC)

Never mind...it turns out it is used [20]. 202.155.85.18 (talk) 01:03, 22 July 2014 (UTC)

Because there ain't no coconuts here in the USA (nor in England, last time I checked, unless that global warming thing really kicked in over there). 24.5.122.13 (talk) 04:04, 22 July 2014 (UTC)

You may want to be careful about claiming there are no alternatives as a previous contributor seemed very concerned [21] about such claims Wikipedia:Reference_desk/Archives/Science/2014 April 1#Wired can't figure out cleansteel. Anyway as others have said it's not necessarily impossible to use other methods [22] [23] [24] [25]. It's more that these methods aren't used much because of cost and similar reasons compared to total annual production [26] (and I believe in the earlier discussion there were figures of 74 million vs about 1.5 billion total production). So as evidence by the previous sources and others like [27] (and of course this infamous article [28]), there's great disagreement over whether it's realistic to expect coke to be substanially replaced in steel production in the next 20 years or so. (And of course, if it is replaced, whether it will be smelting iron with some other carbon or whatever reducing agent whether non renewable like shale gas or renewable like something plant derived, or whether some other method like electrolysis could be used.) Nil Einne (talk) 14:21, 22 July 2014 (UTC)

As I already pointed out above, there are alternative processes which use syngas instead of coal as the reducing agent. And of course it's theoretically possible to use electrolysis, but this is so expensive as to be utterly uneconomic at present (not to mention that most of the electricity it would use is generated from coal anyway...) 24.5.122.13 (talk) 04:18, 23 July 2014 (UTC)

Strength training

Does resting too long between sets during strength training lower it's effectiveness? Why? -- 90.201.185.224 (talk · contribs) 10:59, 21 July 2014 (UTC)

Define "too long". ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:02, 21 July 2014 (UTC)

I tend to rest several decades between sets, and that does, indeed, appear to lower it's effectiveness. StuRat (talk) 16:13, 21 July 2014 (UTC)

It ultimately depends on your goals. When you say "strength training" do you mean, literally, that you are seeking to increase strength in the sense of powerlifting, or do you mean it in the sense of weight lifting, in general? At any rate, the general rule (I'll dig up sources later, I'm at work and not able right now to give more than a few random articles) seems to be that shorter rest periods (say 1 - 1.5 minutes) with high intensity around 8 - 12 reps per set is idle for hypertrophy due to growth hormones, whereas for increasing strength, heaver weights (3 - 5 rep range) with 3 - 5 minute weight periods; this will allow you to do more reps. According to bodybuilding literature, the first is more geared towards sarcoplasmic hypertrophy (more massive) the latter myofibrillar (strength) - although, neither occurs in isolation from the other, it's more a matter of what you want to focus on most, though. At any rate, take all of this with a grain of salt, I've read a lot on the topic, but this is also from memory and typed in a rush. Finally, be aware that these are guidlines that have some support, but ultimately, what is "too much" or "too little" of anything will be a matter of your body, your diet, and your goals - you would be best served talking to a trainer, or just trying various regimes for 4 - 6 weeks and seeing the results over time. Heres a few articles, when I get more time, I'll find some better sourcing for you: [29], [30], [31], [32]. (As mentioned, these are by no means "definitive", take what I say with a grain of salt.).Phoenixia1177 (talk) 13:59, 21 July 2014 (UTC)

Power source

It took many hundreds of years before the invention of electricity, is it envisaged that someone, at some far future date, will invent an entirely new source of power?85.211.132.74 (talk) 12:41, 21 July 2014 (UTC)

We don't answer requests for opinions, predictions or debate. 84.209.89.214 (talk) 12:54, 21 July 2014 (UTC)

There are a few tidbits mentioned in Energy development. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:20, 21 July 2014 (UTC)

Electricity isn't a "source of power" - it's a means for transmitting energy from one place to another. For example, from the energy produced by spinning water turbines in the Hoover Dam is transmitted to the caps-lock LED in your keyboard by electricity. The electricity wasn't the source of the power - that was the water spinning that turbine.

We certainly do have other means to transmit power - for example, the Seattle Steam Company makes steam by using natural gas as an energy source, using it to boil water - and then pipes the resulting steam to local businesses, where it's used to provide heating. No electricity is involved - the energy is transmitted by the steam.

Electricity is a very convenient way to transmit power because we've figured out ways to convert almost any energy source into a flow of electricity - and to use a flow of electricity to power almost any kind of device we can think of. But it's not always the most efficient way - as the Seattle Steam Company have proven. But considered more broadly, an oil pipeline is another way to transmit energy. When you buy candy in your local store and bring them home for your consumption - you're transmitting energy (in the form of food calories) from the store to the place where it's going to be converted into body heat, body motion and brain activity.

SteveBaker (talk) 14:22, 21 July 2014 (UTC)

One could argue that it was nature that invented electricity, we just figured out how to exploit it. The reason it exists and the reason we can exploit it ultimately lead back to the Big Bang. It reminds me of a Carl Sagan statement: If you wish to make an apple pie from scratch, you must first invent the universe. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:33, 21 July 2014 (UTC)

Most people would say that we "discovered" electricity - just as we "discovered" fire. We generally reserve the word "invented" for things like 'The Wheel' - or 'The Internet' which didn't already exist in nature. SteveBaker (talk) 14:55, 21 July 2014 (UTC)

"We don't answer requests for opinions, predictions or debate. <IP address misappropriated>" Apparently not!!

I see, like nature created water power, but humans invented the gristmill and the hydroelectric dam. So maybe the OP's question comes down to whether new energy types might be invented in the future, i.e. if we haven't thought of everything yet? Electricity is generated by a variety of technologies, some old, some new - but it's still electricity. There could be additional fuels for generating electricity which we haven't discovered or made practical yet. But I think the OP is asking whether we have any clue of something that could replace electicity itself. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:24, 21 July 2014 (UTC)

Is there anyone already working on alternative forms of energy transmission? The OP refers to electricity as a "source of power" but I'm not sure this phrase encompasses everything they intend and I can't think of a better one. Would you call the electrons moving around a circuit a "source of power"? Circuits can operate using lasers, right? So light could be a "source of power" in the future, beyond the manners in which it already is? Could long-distance light transmission ever compete with electrical energy transmission in terms of efficiency? Could quantum entanglement play a role in energy transmission and conversion to work? --129.215.47.59 (talk) 14:18, 21 July 2014 (UTC)

Sitting in your home, electricity can be thought of as a "source of power", although that's not true in the big picture. The OP has made only two entries - the original question here, and 5 days ago about the possibility of creating giant batteries.[33] That suggests he's talking about ways to produce electricity rather than alternatives to electricity. But until he returns and comments, it's hard to know for sure. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:03, 21 July 2014 (UTC)

Note that people have been using electricity for thousands of years, although only a few people, and only as a "magic trick". Ancient clay pots seem to have been electrical cells, using acid (vinegar or lemon juice, perhaps), metal plates, and electrodes to create sparks on demand. Not sure if they hooked it up to an electric filament, but, if so, they would have had electric light, at least until the filament burnt up due to the lack of vacuum around it. Of course, an oil lamp would have been far more practical, at the time. StuRat (talk) 16:19, 21 July 2014 (UTC)

In terms of new stuff, there are people looking into using Spintronics as an alternative to electronics - where the spin of the electron is used instead of the charge. I'm not sure if that helps you with energy sources - or ways to transmit energy though.

My problem here is that the OP is asserting that electricity is the "source" of the power...if we're talking about power sources, then sure, we invented ways to use nuclear power (both fusion and fission) long after electricity was discovered and tamed. If we're talking about how energy is TRANSMITTED then we routinely transmit small amounts of energy in fibre-optics or using radio waves but also in larger quantities: A microwave oven transmits power through the air into your food using microwaves. The laser cutters my wife uses in her business transmit about 100 watts of energy through a beam of infra-red light over a distance of around ten feet.

So we have come up with plenty of new power sources - and new ways to transmit power - since the discovery of electricity...which leaves me puzzled as to why our OP thinks that electricity is the most recent discovery in that field. SteveBaker (talk) 16:50, 21 July 2014 (UTC)

StuRat: I think you are referring to the Baghdad Battery, which, according to Wikipedia's article, is no longer believed to have been electrical by mainstream archaeologists. הסרפד (call me Hasirpad) 02:18, 22 July 2014 (UTC)

" We don't answer requests for opinions, predictions or debate. <IP address misappropriated> " Apparentlty not !!

• • Hearing someone chime in with "No one is allowed to answer this question" when it is an appropriate question is a little annoying, like hearing little birds squawking for no apparent reason. Edison (talk) 16:04, 22 July 2014 (UTC)
    • I agree. The questioner asks whether this "is envisaged" - and that's a testable proposition. Are there reliable sources to say that someone notable in the world of physics is envisaging some new power source - and presumably doing research in that direction. SteveBaker (talk) 03:09, 23 July 2014 (UTC)

• "Electricity" is not a source of power and was not invented, but electric batteries are sources of electric power, in the sense that they make electricity from a combination of chemicals. Generators are sources of electric power, in the sense that they translate a prime mover into electricity. Solar cells are a source of electric power as well. The electricity created by these devices is a type of power which has useful properties that the chemicals, the prime mover or the sun lack. In the sense of the OPs question, researchers are always trying to find new ways to convert something into electricity. Micropower describes devices which produce electricity from chemical fuel in a consumer device or a portabl military device, or which produce electricity from sound energy or other less useful forms of energy. Edison (talk) 22:45, 23 July 2014 (UTC).
  • How would you re-word the OP's question so that it makes proper sense? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:50, 23 July 2014 (UTC)
    • I can't - I truly cannot parse what the OP is asking. Are we being asked about new ways to TRANSMIT energy? (Electricity is one way - there are others, like the steam-heat system in New York or (in a sense) an oil pipeline or a fibre-optic cable) - or are we asking about brand new energy sources? (electricity isn't an energy source) Either way, the OP's question doesn't make sense. We need to be asked a question that makes sense. So perhaps:
      1. "What other ways of transmitting energy are being developed or are thought to be plausible in the future?"...or...
      2. "What other sources of energy are being developed or are thought to be plausible in the future?"
    • I can't find a way to wedge "electricity" into the question without destroying it. (1) can't refer to electricity as the only way we transmit energy right now because there are dozens of ways we do that. (2) can't refer to electricity because it's not an energy source. SteveBaker (talk) 04:51, 24 July 2014 (UTC)

But isn't electricity the only way we transmit energy over large distances so that it can be used for something other than heat? I can't be sure what the original questioner was asking but it inspires me to ask what potential forms of transmission of energy might arise from current or future research that can do useful work like calculations, display of entertainment or data, production of sound, washing of clothes, cooking of food. 129.215.47.59 (talk) 10:26, 24 July 2014 (UTC)

I take it you never played SimCity 2000? EM is an obvious possible alternative form of transmission. Microwave transmission#Microwave power transmission is most commonly suggested. Lasers are also sometimes suggested although usually only for specialised cases. We also have an article Wireless power which discusses these possibilities and more although it also discusses stuff like induction used for short transmission distances. Nil Einne (talk) 14:12, 24 July 2014 (UTC)

Natural gas can be used for things other than heat. It can be used to run a generator or fuel cell to create electricity, or can directly power heats pumps, etc., to provide cooling. It tends to be more reliable than electricity from the grid, is also maybe a third the cost of electricity per unit of energy, in many places, and fracking may bring the cost down further. StuRat (talk) 14:21, 24 July 2014 (UTC)

Strength vs cardio training

Does strength training have the same health benefits as cardio training such as promoting good immune system health, heart health etc.— Preceding unsigned comment added by 90.201.185.224 (talk) 16:23 21 July 2014 (UTC)

Certainly not as much benefit for the heart as cardio, but still any exercise is better than none. StuRat (talk) 16:41, 21 July 2014 (UTC)

It's possible to overtrain or improperly train, and this can be unhealthy, even for athletes. UFC fights are routinely cancelled/changed for training injuries. That sort of exercise isn't better than nothing. Unfit people should always start off slower than fitter folks. InedibleHulk (talk) 03:05, July 23, 2014 (UTC)

Here are some references about how strength training can improve various aspects of heart health [34] [35]. The benefits of strength training for heart health seem to be different than the benefits from cardio. SemanticMantis (talk) 18:06, 21 July 2014 (UTC)

July 22

Can anyone identify this bird?

I would like to upload this somewhat accidental pic I took to Commons, but I can't identify the bird. It's the eye colour that defeats me. Can anyone help? It was taken a few weeks ago a couple or miles or so inland from one of the wilder reaches of the west coasts of the EU on an old train embankment in a wooded area. The eye colour is natural as I wasn't using fill-in flash. Help really appreciated. Coat of Many Colours (talk) 00:07, 22 July 2014 (UTC)

I think it's a Tit. Not sure which one, though. --Jayron32 00:39, 22 July 2014 (UTC)

Indeed there are some red-eyed Tits around, thanks for that. Coat of Many Colours (talk) 01:06, 22 July 2014 (UTC)

It's a Dunnock — quite common in that part of the world! MeegsC (talk) 01:26, 22 July 2014 (UTC) (from WP:BIRDS)

Brilliant! That's it exactly. I had no idea they had red eyes. Not exactly twitcher event of the year thus, but still it gives me pleasure. He was just perched a metre or so away from me and quite unafraid and at last I was able to get decent shot of a bird. Thanks so much. Coat of Many Colours (talk) 06:24, 22 July 2014 (UTC)

Happy to help. They're brilliant little birds. And it's always fun to get a great shot! MeegsC (talk) 12:00, 22 July 2014 (UTC)

Life flashing before one's eyes

Is there a term for it? Is it covered somewhere? I don't see it being covered in near-death experience. Anna Frodesiak (talk) 00:28, 22 July 2014 (UTC)

Life review, though I haven't looked at the article. Huge admirer of your user page by the way. Coat of Many Colours (talk) 00:36, 22 July 2014 (UTC)

This also might interest. Coat of Many Colours (talk) 00:39, 22 July 2014 (UTC)

Wow! Sooooooooo spooky. Thank you kindly. I expanded the description and made a couple of redirects. And thank you for the compliment about my userpage. :) Anna Frodesiak (talk) 00:51, 22 July 2014 (UTC)

Pleasure. Coat of Many Colours (talk) 01:04, 22 July 2014 (UTC)

Skyglobe replacement

I want an application that will serve the same as Skyglobe, but I don't know what to call it, so I can't run a decent Google search; all I've been able to find so far is stuff such as Terrestrial Planet Finder, which obviously is not a program I can use to figure out what's in tonight's sky. Any ideas? I downloaded and extracted the ZIP file for Skyglobe, but upon telling it to run the Windows version (I have Windows 8) of the program, all I got was a message of "this program cannot be run on your computer", so I need something else. Nyttend (talk) 02:57, 22 July 2014 (UTC)

The only one I'm familiar with is RedShift (planetarium software) — (current version 7) –There are several others listed on Planetarium software; and a more complete list can be found here, on AstronomyOnline.org (neither list mentions Win8, however).  ~:71.20.250.51 (talk) 06:04, 22 July 2014 (UTC)

I'm not sure I've got all the nuances of your question, but Stellarium (computer program) is a tremendous program. I run it on Windows 7 but it claims to run on Windows XP or greater. (BTW I've recently discovered Google Sky Map for Android). Thincat (talk) 21:23, 22 July 2014 (UTC)

Starry Night runs on windows 8 (but not W8 RT). I've found the cheapest version to be excellent. As Thincat says, if you want something for free, google sky map on a smartphone or tablet is brilliant. Hold it up to the sky and it shows you an annotated image of the section of sky you're pointing it at - and as you move the phone the image moves too. Richerman (talk) 14:00, 24 July 2014 (UTC)

Base hydrolysis

Do thioethers and alkyl arsenides/arsenates undergo hydrolysis in concentrated alkali solution? (For that matter, do amines do so?) Thanks in advance! 24.5.122.13 (talk) 04:07, 22 July 2014 (UTC)

Answer to question 1. --Jayron32 04:14, 23 July 2014 (UTC)

Thioethers, not thioesters (I already know the latter hydrolyze readily). In case you're wondering, here are my three reasons for asking. (And just so you know, my educated guess would be that alkyl arsenides and thioethers hydrolyze, but amines don't -- but I can't find reliable info to either confirm or refute it.) 24.5.122.13 (talk) 09:11, 23 July 2014 (UTC)

Identification of the species

Species name?

Can someone help me with the identification of the species? Thanks in advance. Nikhil (talk) 05:40, 22 July 2014 (UTC)

So, from your image title, I'm guessing that this specimen was found in "Blossom International Park" - about 3 Km from the town of Munnar in India. (That kind of information *REALLY* helps with identification problems). I did a Google Image search on the name of the park and got a bazillion photos of various flowers...I hoped to find a picture of the flower in your photo which someone might have helpfully labelled - but no such luck. Sadly, the park is renowned for the enourmous range of exotic flowers it has...which isn't exactly helpful! If you have a picture of the plant from further back - so we can see the general shape of the plant - that might help. SteveBaker (talk) 14:53, 22 July 2014 (UTC)

Where in the world was this taken? Was it a garden or wild? When was it taken? How tall was the shrub? Answers to these questions will help identify the flower. As it stands, I might guess a white azalea, but that's just a guess. SemanticMantis (talk) 14:38, 22 July 2014 (UTC)

• @SemanticMantis Thanks for the response. It was taken in Kerala, India. It was taken in a flowers park, sort of exhibition for all the flowers. Shrub was about 1 to 1.5m tall. Nikhil (talk) 14:51, 22 July 2014 (UTC)

Reaction

If p-aminophenol is reacted with acetic anhydride, what is the product? Is the amino group acylated or the hydroxy group? 49.183.254.235 (talk) 06:36, 22 July 2014 (UTC)

The hydroxyl group is more reactive, so it should be acylated preferentially. So the product will be mainly the acetic ester, with possibly a small amount of the amide. (Note that in the presence of an acidic catalyst such as aluminum trichloride, yet another reaction can occur, placing the acyl group on any of the four remaining aryl positions, but preferentially (but not exclusively) ortho to the amino group -- so you'd now end up with a total of up to four different products!) 24.5.122.13 (talk) 08:35, 22 July 2014 (UTC)

Although the article Paracetamol disagrees with me, giving the amide as the main product. Maybe this depends on the reaction conditions? 24.5.122.13 (talk) 08:51, 22 July 2014 (UTC)

Is the amino group more electronegative? 49.183.254.235 (talk) 09:49, 22 July 2014 (UTC)

As a rule, oxygen is more electronegative than nitrogen. 24.5.122.13 (talk) 00:05, 23 July 2014 (UTC)

Inertia Simple expiation needed thank you.

Confused my self on it. Please be patience with me thank you. Inertia and what it means is driving me crazy. Ok my question is: if Inertia is the property of mater and for the sake of argument that it is stationary. lets call this first object a tree stump. Then if another object comes along moving at high speed (velocity right?) Then should this moment be called inertia? or momentum? or energy? I'm missing something here. Am making a book and trying find the correct word, and have been stuck on using inertia correctly, I tend to think backwards on some things if that makes an sense.

Here is where I'm having a problem:

Ignoring him she continues to sprint over the surfaced of the lake! Half way into the lake, making a v-turn and going up a hill. And then they go through another valley. Near a long mountain range she lets go of his hand. - Inertia propels her forward - into a stump near by with a bone-crushing smash! Parcival runs over to her. Hurriedly kneeling down afraid to touch her.

Ignoring him she continues to sprint over the surfaced of the lake! Half way into the lake, making a v-turn and going up a hill. And then they go through another valley. Near a long mountain range she lets go of his hand. - The momentum propels her forward - into a stump near by with a bone-crushing smash! Parcival runs over to her. Hurriedly kneeling down afraid to touch her.

Ignoring him she continues to sprint over the surfaced of the lake! Half way into the lake, making a v-turn and going up a hill. And then they go through another valley. Near a long mountain range she lets go of his hand. - Her energy propels her forward - into a stump near by with a bone-crushing smash! Parcival runs over to her. Hurriedly kneeling down afraid to touch her.

So what one of these three is correct? Thank you so much if you decide to help me. I should know this stuff my by now, but guess I've forgotten what it means exactly. Help please. — Preceding unsigned comment added by 173.18.147.198 (talk) 15:43, 22 July 2014‎

None are correct. If she were a rocket, circling the Earth, with no propellant left in the tanks, she would not be propelled by it. So she is not propelled by inertia, momentum, nor force, but merely continues moving relative to the ground. Wnt (talk) 17:27, 22 July 2014 (UTC)

A better example is this: "...she lets go of his hand, but continues moving forward. Why? She has inertia." Inertia means resistance to change. --Bowlhover (talk) 18:20, 22 July 2014 (UTC)

As pointed out above, "propel" is a problematic word, because propulsion is a matter of accelerating an object via the application of a force, but you're trying to describe the behavior of an object in the absence of a net force. And "energy" provides an insufficient explanation of the behavior, because energy is a scalar quantity, so the conservation of energy alone doesn't preclude the possibility of the object changing direction while maintaining the same speed; see kinetic energy. The full behavior of the object continuing in a straight line at a constant speed can be described as either being an example of the law of inertia, or as being an example of the conservation of momentum. Red Act (talk) 20:26, 22 July 2014 (UTC)

The usual phrase is "her momentum carries her forward". Dbfirs 20:49, 22 July 2014 (UTC)

Your problem is that you want to describe something we easily understand, a painful collision of a running lady with a tree stump, but have introduced technical terms of physics such as inertia momentum and energy in your narrative. I think it is unnecessarily pedantic to analyse the collision in these terms but here are their rôles in the collision:

• Inertia is the resistance of any physical object to any change in its state of motion, including changes to its speed and direction. The lady has forward inertia. In non-technical storytelling I don't object to "Her inertia propelled her forward into a stump..". This is just the literary device of making an active verbal statement where as Wnt points out, there is no actual propellant. However general readers tend to associate inertia more with absence of movement than persistence of movement, which is not the right association here.
• Momentum is the product of the mass and velocity of an object. The lady has forward momentum. This means the same as inertia except that momentum is a numerical vector quantity. Likewise it's possible to say "Her momentum propelled her forward into a stump..". However the resulting collision is not the elastic type that conserves momentum so you are using the word colloquially, not technically.
• Energy is a numerically calculable property of matter that comes in many forms. In the story, the lady has Kinetic energy ${\begin{smallmatrix}{\frac {1}{2}}mv^{2}\end{smallmatrix}}$ until she meets the stump. That energy then converts into other forms of energy such as heat, noise, vibrations and bone fracture. Such analysis does not make for good storytelling.

It would be simplest to forget the exact physics, write "She broke free from his grip and flew into a stump with a bone-crushing smash" and get on with the rest of your book. 84.209.89.214 (talk) 21:30, 22 July 2014 (UTC)

There is some subtlety to this description. Newton says that objects remain in their state of motion unless disturbed by a force. So she keeps on moving because that's what things do if you don't go sticking a tree-stump in front of them! In terms of the physics, nothing special is happening to her as she continues to move. Her constant state of motion is due to the LACK of any other influences. We don't need a name for what changed - because nothing changed.

If you want to be scientifically pedantic, then having a "high speed" is the correct terminology. A "high velocity" is a rather meaningless term because velocity is speed combined with direction - and "high" versus "low" is hard to say when a direction is included. So, actually, "speed" might be the better word.

But then, we could invoke relativity and say that it's not even meaningful to talk about the person's velocity/speed because it is equally valid to state that she is "stationary" and it is the tree stump that is moving "at high speed"...and then the only true description is to say that the person and the tree are moving relative to each other at high speed.

When viewed like that, you can't even say which object has kinetic energy, or momentum or inertia - it's all a relative matter. From the perspective of the tree, the person has lots of kinetic energy and is moving pretty fast. From the perspective of the victim, the tree stump has kinetic energy and is moving alarmingly quickly.

Fortunately, in a location such as the surface of the earth, we have a convenient verbal convention, which is to discuss motion in a frame of reference in which the earth is stationary...but its' only a verbal convention - and if you're discussing the motion of (say) the moons of Jupiter - it would be singularly perverse to do so with the earth-is-stationary frame of reference.

It follows that when we discuss how someone flies through the air and whacks into a tree stump, we put enough verbal short-cuts into the explanation to keep things comprehensible. Trying to sound more 'scientific' brings with it some fairly extreme inconveniences.

SteveBaker (talk) 04:39, 24 July 2014 (UTC)

Help identifying a dragonfly

File:Unidentifed dragonfly.jpg

Can anyone identify this dragonfly. Taken in Yellowknife, Northwest Territories. Wasn't able to measure it but they are about 150 mm (5.9 in) long. The black item behind it is a tyre. Thanks. CBWeather, Talk, Seal meat for supper? 16:58, 22 July 2014 (UTC)

It must be from the Anax genus. It resembles Anax imperator, the Emperor dragonfly, but our article suggests that they are smaller, and unlikely to be found in Australia. AndyTheGrump (talk) 17:15, 22 July 2014 (UTC)

Well, it's a good thing this dragonfly was photographed in Canada then... --Jayron32 17:17, 22 July 2014 (UTC)

Doh! Sorry, brain slipped out of gear... AndyTheGrump (talk) 17:34, 22 July 2014 (UTC)

CBWeather, are you quite sure about the size? I can't find evidence of any species that big being found in Canada. Incidentally, I may have been premature in identifying it as Anax - it could be another of the Aeshnidae family - possibly Aeshna. AndyTheGrump (talk) 19:09, 22 July 2014 (UTC)

Just asked my daughter, she was there as well, and after a few comments about my eyesight and age it is more likely to be 75 to 100 mm (3.0 to 3.9 in) long. I noticed that in the Emperor (dragonfly) article that the males are difficult to approach but these were easy to get up to. Is it possible it is some variety of darner, Aeshnidae or Aeshna? CBWeather, Talk, Seal meat for supper? 04:22, 23 July 2014 (UTC)

Yeah, that seems likely, looking into this further - though apparently the darners can be very difficult to positively tell apart. I think it may possibly be Aeshna eremita, the Lake Darner - see the image here [36] AndyTheGrump (talk) 06:06, 23 July 2014 (UTC)

Thanks. I'll ask User:Dger as he is the one who uploaded the image in the article. 22:38, 23 July 2014 (UTC)

Swarms of Antarctic krill

The introduction to the Antarctic krill article notes that its swarms can reach a density of 30,000 individual animals per cubic metre, and that the animal itself can grow to a length of 6 cm. Given that there are 1,000,000 cubic centimetres in a cubic metre, and that the image shows the length as several times the other two dimensions (let's guess 5mm height and width), we're left with something like 45,000 of those 1,000,000 cubic centimetres being occupied by the krills' body volume. How do all of them survive, let alone go anywhere in the swarm? Imagine a huge room in which 5% or more of the volume is occupied by humans (e.g. the ceiling is just tall enough for an average-height human, so we can pack the whole volume without stacking people): there's not going to be anywhere near enough food to eat (after all, krill don't have supermarkets or pizza delivery), and without verbal communication, those humans are going to have a massively hard time going anywhere all together, especially if we remove the walls and ceiling. How are krill able to do it better than humans? Nyttend (talk) 23:51, 22 July 2014 (UTC)

To me a "swarm" isn't the density at which they normally live, any more than a "crowd" of humans is how we normally live. Presumably they just pack together occasionally for certain purposes, like mating.

Also, since they are filter feeders, their food is delivered by the water itself, so they don't need room to farm, herd, etc., like people do. Now, if you had a cubic kilometer with them all at that density, then I would expect that the center of that cube would starve, but if spread out over long "tendrils", they should have more access to food washing in from the sides. StuRat (talk) 23:57, 22 July 2014 (UTC)

The article said that "swarm" was the term for their schools, so I was imagining something like schools of bigger fish, a massive "blob" (large in all three directions) of fish all actively swimming together, rather than a group mating but not going anywhere or a massively long string or otherwise essentially 2-D group. Did I have the wrong idea? Nyttend (talk) 00:07, 23 July 2014 (UTC)

Consider that krill in large groups don't have to deal with the problems of body heat, sore legs and the various mammalian (and distinctly human) social anxieties that come with those, like a crowd of people do. If someone's in their way, they can far more easily go around, over or under. Water is cool that way. InedibleHulk (talk) 03:13, July 23, 2014 (UTC)

Of course, when you're moving as a unit, the problem of people in your way isn't so common. Compare marching soldiers to a similarly sized concert audience. I'd assume time moves slower for those tiny krill, so what may be seen as rapid commotion by our eyes should be much more relaxed on their level. If you've never seen a giant cloud of bats leave a cave, I recommend it. Almost unbelievable how they don't all crash and die. InedibleHulk (talk) 03:22, July 23, 2014 (UTC)

@Nyttend:Several benefits of Schooling_(fish) apply to krill as well as fish. Flocking_(behavior) gives some clues as to how this is accomplished by organisms without much of a brain or communicative capacity. Basically, all each one has to to is swim vaguely in the direction of another that it can perceive, and (modulo some tuning of parameters), coherent motion is achieved as an emergent process (see also Self-organization, and perhaps ant mill).

Contrary to your notion that the swarm has less food, aggregation can serve to increase feeding efficiency. It can also serve to reduce predation by slightly larger organisms, though of course whales and such take advantage of the swarms to increase their feeding efficiency. These concepts are elaborated in the schooling article. Another thing to keep in mind is that water "feels" much different to krill compared to cod or humans, because of the differences in Reynold's number. This means it's really hard for krill to bump into each other. Does this explanation make sense?

To your follow-up question, my understanding is that the density quoted is something like a seasonal max. Not all krill are always 'swarmed', and not all swarms achieve that density. But many swarms exist as coherent aggregations at any moment. I'm not an expert on krill, but that's my reading as a biologist.

Finally, is 5% by volume really that dense? If we take average human volume to be 0.0664m^2 and average human height to be 1.6m (via wolfram alpha [37]), then that puts ~120 people in a room with dimensions 10mx10mx1.6m. Looking only at area, that's ~0.83 m^2 per person, which is far less crowded than a modern lecture hall or a bus at rush hour, to my estimation. SemanticMantis (talk) 14:56, 23 July 2014 (UTC)

July 23

Are all spontaneous processes exothemic?

According to the article Spontaneous process, a spontaneous process should be exothermic as said by the first lines

"A spontaneous process is the time-evolution of a system in which it releases free energy (usually as heat) and moves to a lower, more thermodynamically stable energy state."

But I think the statement is wrong. Because ice melting is an endothermic but spontaneous process at room temperature or even at or above 273 K, some spontaneous processes should be endothermic. And when glucose is dissolved the water becomes cooler. But glucose melting is spontaneous. Should enthalpy get confused with entropy? When ice melts ice absorbs some heat from the surrounding. Please give your comments. A user has already pointed out this in the article's talk page. But there were no response for 3 years. I asked this here to get some response.--G.Kiruthikan (talk) 10:47, 23 July 2014 (UTC)

Further down the article, it specifies "free energy" to refer to Gibbs free energy. Plasmic Physics (talk) 11:47, 23 July 2014 (UTC)

Natural Selection

Could it be argued that those who get bullied or those who end up single for life, not by choice but as a result of shyness or women not finding them attractive etc, are experiencing a process of natural selection, favouring those who are confident and can stand up for themselves?

This is called sexual selection Graeme Bartlett (talk) 11:48, 23 July 2014 (UTC)

It ultimately benefits humanity, by ensuring a continued supply of Wikipedia editors. 80.43.213.39 (talk) 12:03, 23 July 2014 (UTC)

wouldn't that be called Wikipedia selection,

There is nothing good or bad about natural selection, it is just what happens in the circumstances. Our circumstances are that we have laws and a belief in rights and basically a complex society. What that will lead to is anybody's guess. For instance currently deaths by firearms and deaths from car accidents are at a rate that very probably will have an effect on our genome but we can't guess what it will be. For all we know the characteristics that lead to bullying may be preferentially removed by them being involved more in such fatalities. I'm not altogether sure though if that was the case that we should then say we should remove car and gun safety laws. Society is the environment for evolution now. Dmcq (talk) 12:48, 23 July 2014 (UTC)

I should apologize in advance for blatant speculation, but just thinking out loud... I recently saw a study in which the frequency of homosexuality was listed as only 1.6%, and only 2.5% even when bisexuality is included. The figures for this used to be much higher, starting with the famous Kinsey Reports figures of 10% and 37%, but every decade they seem to get lower. I would suggest that this may not be experimental error; rather, the effect of anti-gay oppression may have been to pretty much force people to reproduce who wouldn't have otherwise. (The irony of this effect should not much shock those who have seen obscure plants like Cannabis turned into household words over the past century) The present figure is still greater than the (somewhat inflated) figure for autism, so by this model I'd expect the frequency to drop several-fold more over the next few generations. Anyway, if any of this is true then I would expect any other genetic trait whose effect on reproductive success was concealed by social compulsions to reproduce would likewise be uncovered by the same change in attitudes, and to be undergoing a similar reduction in frequency. Wnt (talk) 12:54, 23 July 2014 (UTC)

it only takes a single exception, you could be a lonesome reject for life except meet 1 bookworm after 17 years of nothing post-puberty, and it's literally all it takes to procreate, get married, etc. Think about your parents :) Or their parents. In fact you come from a direct line of pushovers who all successfully procreated, going back tens of thousands of years. You'll probably end up married yourself (chances are). So zero evolutionary pressure here. 213.246.165.17 (talk) 14:42, 23 July 2014 (UTC)

• Anything that influences the probability of ultimately having children is going to create selection pressure. But it is important to realize that natural selection operates on a time-scale of thousands of years, whereas human social systems affect us on a time-scale orders of magnitude faster. The consequence is that natural selection is almost never a significant factor when thinking about how our social systems ought to be structured. Looie496 (talk) 14:53, 23 July 2014 (UTC)

That's not true though. Peppered moth evolution changed the color of the peppered moth from specked white to totally black within 50 years - and back again within another 50 years. Evolution can produce an effect within just one generation if the selection pressure is sufficiently harsh. A sufficiently decisive social movement could easily wipe out a particular single-gene variation in just a few generations.

The thing that makes the "lonesome bookworm" type succeed is that there are other lonesome bookworms of the opposite sex who really couldn't stand to hook up with someone with a loud, outgoing, sport-enthusiast "Type A" personality. So there will always be enough pairings to ensure that the type survives. The question worth asking is how long it'll be before "homo sapiens geek" become a separate species from the "homo sapiens jock" ? SteveBaker (talk) 16:59, 23 July 2014 (UTC)

If the jocks get the pretty girls and the geeks do the technology then it should have been the Eloi in the Time Machine who were the brutals not the Morlocks. ;-) Dmcq (talk) 17:27, 23 July 2014 (UTC)

I'd probably think a bit more about generation time of moths vs. humans before claiming that Looie said something wrong about evolution. Nothing about natural selection has an absolute time scale-- the widely variable and natural unit of time is the generation, because that's where mutation and selection happen (for simplicity ignoring the case of horizontal gene transfer). Peppered moths have 1 generation per year at minimum, humans of course go much slower. So 50 human generations may well be enough time for some of us to get spots or whatever, but that's still a much longer time scale than most of our social structures have. You are of course correct that strong selection can have a decent effect in just one generation, but that would be very strong selection indeed, and I think we'd all agree that that is not what this question is about. SemanticMantis (talk) 18:25, 23 July 2014 (UTC)

I'm a geek. My wife is beautiful. HiLo48 (talk) 20:01, 23 July 2014 (UTC)

--Bowlhover (talk) 23:35, 23 July 2014 (UTC)

I'm a geek. My wife is also a geek. We both agree that intelligence, wit, honesty, gentleness - and most of the other thousand attributes that make for a good marriage - *all* trump beauty. (Although, as it happens, she's also beautiful!) SteveBaker (talk) 04:25, 24 July 2014 (UTC)

Is there any evidence that there a large pool of 50 year old male "geeks" who yearn to be fathers, but haven't succeeded in fathering offspring? Cullen³²⁸ Let's discuss it 05:10, 24 July 2014 (UTC)

Probably not - but I guess the real issue is whether there are a large pool of 50 year old geeks of either gender who don't yearn to be parents? SteveBaker (talk) 16:07, 24 July 2014 (UTC)

But realistically, for this kind of 'geeky' person to evolve out of existence, you'd have to assume that 'extreme-geekiness-leading-to-not-having-kids' has a genetic basis - and that it's a simply-inherited one that comes from just a few genes that aren't 'mission critical' for anything else. It could easily be that you turn out to be a geek because of some complex mix of genes, then maybe you have one great grandmother had blue eyes, one great grandfather had a club foot, at least one other great grandfather was NOT color blind AND another great grandmother carried the genes for both sickle-cell anaemia and lactose intolerance. If the situation is that complex then the trait of geekiness isn't going to pass directly from one generation to the next and it would be unlikely to vanish from the gene pool no matter how bad we geeks are at reproducing.

Sickle-cell disease is another good model to consider. If you have a sickle-cell gene from both mother and father, then (without modern medicine) you're unlikely to survive long enough to reproduce - you'd think that this defect would have vanished from the gene pool tens of thousands of years ago. BUT having just one of these genes confers immunity from malaria. So the benefit of being a 'carrier' of sickle-cell outweighs the risk of producing sickle-cell children that die early...so the gene stays in our gene pool.

Complex genetic outcomes are much more complicated. For example, if there is a genetic component to living on into old age - that couldn't directly affect the gene pool because the gene doesn't improve reproductive success because it only does something after you're too old to have kids. If that were all there were to this, then humans would drop dead the moment they were no longer able to reproduce (that happens with LOTS of other animals). But in fact, we're social animals and an entire village gains reproductive success if there are some older people around to pass on knowledge and so forth. So the presence of the gene for living longer has value to the reproductive success of the population, and it is selected for to some degree.

If small communities see reproductive benefits from having geeks around to figure out why their PC won't run Candy Crush anymore - then the genes for geekiness will remain in the population

even if no geek ever has a child.

SteveBaker (talk) 16:07, 24 July 2014 (UTC)

can a clear substance become opaque upon electrical impulse?

Hi,

Can a transparent substance become opaque upon electrical impulse? For example glass that can become frosted (or in any other way not-transparent) upon electrical impulse?

213.246.165.17 (talk) 13:38, 23 July 2014 (UTC)

An LCD sort of does this. RJFJR (talk) 13:46, 23 July 2014 (UTC)

Why do you say "sort of"? Would this work to darken a room for example? (Like, instead of shades.) Is the level of transparency adjustable? 213.246.165.17 (talk) 13:53, 23 July 2014 (UTC)

See Smart glass#Electrically-switchable smart glass. I don't know whether any of these technologies can be used to make glass perfectly opaque (and I didn't read enough of the article to find out), but your mention of "frosted" implies at least some translucency. Deor (talk) 14:04, 23 July 2014 (UTC)

If this is just an LCD, what keeps someone from just bulding up thousands of layers of LCD screens for a true volumetric display? 213.246.165.17 (talk) 14:24, 23 July 2014 (UTC)

Most LCD screens (not the ones referred to above) use two crossed polarizing filters so there's no way I can see to stack them meaningfully. Transparent OLED is probably the closest to what you want but it is nowhere near transparent enough and can't give dark colors for points. Dmcq (talk) 14:54, 23 July 2014 (UTC)

Display device lists various 2D and 3D display types. Dmcq (talk) 15:05, 23 July 2014 (UTC)

I've thought of this idea myself, as a way to control solar heating of a home. Because of the cost and lack of total transparency I rejected LCDs as the way to achieve this goal. I believe they do make electrically operated miniblinds between panes of glass, and making on side reflective (either white or silver), and the other side black should provide the maximum difference between open (when you want both heat and light), closed with black side out (when you want heat, but not light), and closed with reflective side out (when you want neither heat not light). Certainly it wouldn't block 100% of the light, though. An advantage over LCDs is that it would only use electricity when moving the mini-blinds, and very little then, relative to LCDs which would use electricity the whole time they are on. Also, LCDs don't seem able to withstand wide ranges in temperatures, which you should expect at windows.

Another option might be electrically operated window shades. If those could also be placed between panes of glass, hopefully the edges could be held firmly in place, so light doesn't leak around them as it does through a mini-blind. StuRat (talk) 15:28, 23 July 2014 (UTC)

What would be a way to get a true volumetric 3D display using such technologies? (i.e. that changes depending on the angle you view them at, where one layer can occlude another layer, etc) 213.246.165.17 (talk) 15:55, 23 July 2014 (UTC)

Well, if you DID have a material where individual pixels could be turned opaque or transparent on command without doing polarization tricks - then you could make a bunch of layers and have some sort of voxel-based 3D display. But for even a very low resolution display (say 640x640x480) you'd need 480 layers! Unless these layers are amazingly cheap, you'll have a fairly crappy display costing a good fraction of a million dollars!

Worse still, a 640x480 2D image only looks reasonably acceptable because it's typically "antialiassed" to get rid of the jaggy edges by making fuzzy transitions from regions of one color to the next. You can't really antialias a volumetric display - so even a display with hundreds of layers would be very 'blocky' looking.

I'm not sure if it's currently possible to electrically opaque individual pixels in a panel - but no matter because unless there is some kind of major technological breakthrough it would be prohibitively expensive. Another issue would be the reproduction of color - and to make convincing 3D, you'd probably need programmable shininess, partial translucency and other surface attributes. The way that light interacts with a surface is critical - and these blocky 'voxels' aren't going to do it right!

SteveBaker (talk) 04:19, 24 July 2014 (UTC)

How about a technology where you have one solid block of normally transparent material, that reacts to a certain level of radiation by becoming opaque, then it fades back to transparent in, say, a hundredth of a second after the radiation level drops below the required level ? The device would then aim multiple narrow beams of the appropriate frequency of radiation at each voxel, in turn. Obviously you would want a form of radiation that's not harmful to humans. Creating electromagnetic interference could also be a problem, but you might put the whole thing in a Faraday cage to prevent that. StuRat (talk) 04:37, 24 July 2014 (UTC)

Our volumetric display article briefly touches on this method - using lasers to create points of plasma in air. Katie R (talk) 13:08, 24 July 2014 (UTC)

That only works because the air remains transparent enough to transmit the laser light. What you see with those displays is a ghostly glowing object...it doesn't look solid. When you demand that the voxels become opaque - that would (presumably) block the laser light - so you couldn't make solid-looking objects that way. This is the real problem with most 3D display technologies - it's easy enough to generate those kinds of ghostly glowing images that you can see right through - but they don't look real because you can see distant parts of the object through the nearer parts. There are plenty of ways to make those kinds of displays - holograms, vibrating mirrors, spinning 2D display panels...etc, etc. SteveBaker (talk) 15:13, 24 July 2014 (UTC)

Holy cow, I disagree with every single assumption you've stated. In the first paragraph, you assume that 480 layers and the electronics to drive them would cost a "good fraction of a million dollars", but even at $2000 for the kit (which I would not say is a "good fraction of a million dollars") that is $4 per layer, whereas an 640x480 LCD layer plus everything to drive it (zero economies of scale) costs around $5 at scale, there is no way you couldn't put 480 of them on top of each other at significantly less, at volume manufacturing scales. So this assumption is just totally wrong.

In your second paragraph you say that 3D voxels couldn't be antialiased, but why the hell not? Here is antialiasing with legos: http://brickplayer.com/blog/wp-content/uploads/2010/05/lego_mosaic_anti_alias_3.jpg - why couldn't the same thing be done in 3D? (I realize that most lego sculptures don't use this effect, as they like the blocky effect and don't use that many shades of color anyway - but as a long as the transparency was't binary but had degrees, you could do this.)

In your third paragraph, you assume that voxels have to have real-world properties to "look right". But no pixel has real-world shininess or reflection, and things still look OK on monitors, despite being reduced to a few brightnesses of a few colors. Sure it won't look like the real world, but that is no objection to making voxels. It will look like something.

Finally I will say that despite your analysis being totally wrong, based on clearly false assumptions, I will grant that layers of OLED's or similar is probably NOT the way to do it. Then again, I doubt anyone in CRT era would have thought physically putting 4 million physical pixels - each containing a complete mix of colors - into a 15 inch monitor at 227 dpi was in any sense viable - surely scanning across is the only viable method. And yet that's exactly what a Retina Macbook contains, in a tiny light form factor, as opposed to a phosphor screen and scanning laser. So just because something seems ridiculously infeasible does not mean it is not *the* solution in the future.

All that said, I don't necessarily think layers of LCD's or OLED's or anything else is the correct way forward in the future with 3D volumetric display. I was more interested in the theoretical possibilities, and bringing up technical objections at this thought-experiment stage is unwarranted, especially when the analysis isn't even correct. 213.246.165.17 (talk) 12:50, 24 July 2014 (UTC)

Sadly, my job is doing this kind of thing...so I happen to know that you're wrong. You can't just stack panels like that because they emit heat and the heat buildup in the inner layers would kill you. You need some way to communicate the heat from the inner layers to the outside world. Flat panel displays need bulky connectors and external drivers that don't stack up so well and DO add to the cost. Just the panel itself is only a small fraction of the cost here. I can't think of any consumer-grade gadgets with 640x480 displays that cost $5.

But let's say you're right...$5 display panels aren't THIN. If we want to build a 640x640x480 display that's a few inches across - then we need each layer to be about 1/100th of an inch thick. Do you have any clue how much a 1/100th inch thick LCD panel costs? You want to guess? Please don't - I know the answer - and that's why the cost of your layered display *WILL* be a substantial fraction of a million dollars. Sure, you could build a 640x640x480 display that's (say) 48" thick with 1/10" thick layers - but still, you don't get 1/10" thick panels for $5. With $5 displays, you find them to be around 1/4" thick...so with 480 of them stacked up, you have a display that's 120" thick. Well, if you want a roughly equal resolution/dimensions in X, Y and Z - you now need $5 panels that are 1/4" thick and 10' x 10' wide! I don't think so! So quit talking without thinking.

Yes, antialiassing is a problem. You only want those semi-transparent voxels at the profile edge of the objects - and that's view-dependent. If this is a view-independent display then the objects would have to be 'coated' in all directions with semi-transparent voxels, blurring and fuzzing absolutely everything. When you actually look into this in detail, it doesn't work. Your link to a 2D lego mosaic proves nothing. Your lack of understanding about the issues of light reflection in a 3D object require a longer explanation than I really want to give here - but suffice to say that a 2D representation of a 3D object has already undergone lighting calculations (well, unless it's a very flat cartoon) - and therefore the 2D display surface itself doesn't have to undergo illumination. But a true volumetric 3D object would have to interact with the room lighting or it can't be view-direction independent because the way light reflects off of a surface depends on where you are viewing it from. Since it's really just an array of little cubes, their faces wouldn't align with the light direction the way a real object would - so the resulting lighting would be decidedly strange. Perhaps that would be OK for some kinds of limited applications - but for general 3D display, it would pretty much suck.

Your analogy with the growth of 2D display resolutions isn't exactly correct - when you double the resolution of a 2D display, you only need four times the number of pixels. But pushing the resolution of 3D displays would require not just 8x the number of pixels but it would increase the number of layers that you need...DECREASING the thickness of each layer in proportion to the required resolution. While flat panel displays have shrunk somewhat in thickness over the years - it's not anything like the shrinkage you'd need here. There are no display technologies that are thin enough to generate a small display with reasonable Z resolution - and no thicker displays that are large enough in the X/Y direction to make a large volumetric display. Since the demise of the CRT, the technological improvements to make displays THINNER or LARGER lag by far the technologies to push the resolutions up. It turns out that there are very good laws-of-physics reasons why that is.

So, no - you're the one who is wrong in almost every regard. SteveBaker (talk) 15:13, 24 July 2014 (UTC)

The other issue that stood out to me is the issue of light transmission through each panel. They aren't perfectly transparent, so voxels far away from the viewer will be foggy. Minor imperfections in the plane cause the layer to work like a lens, distorting the path of the light through it. It doesn't matter on an LCD display where the only thing behind the panel is a backlight, but a panel behind 100 layers will be distorted and blurry. Both of those can theoretically be engineered around to make things acceptable, but will obviously cost a fortune. Katie R (talk) 15:54, 24 July 2014 (UTC)

I don't understand why a view-independent object is supposed to have to interact with the room lighting (outside the 3D display) whereas a monitor (normal 2d one) doesn't... We're not trying to trick someone into thinking that a real object is there - you NEVER think your monitor actually has a real object inside it - maybe an ant crawling across it or a hair on it or something - we just want something there, clearly different from a real-world object. Basically, in the sense that a set of pixels is an "approximateion" (a very poor one) of a piece of paper, in that it has different splotches of color at various places, is there a set of voxels that is physically an "approximation" of a paper statue, in that it has different splotches of color at various places, but they also occlude each other? A piece of people is approximated by rows and columsn of pixels. Could a similar theoretical solution approximate a 3d statue, by literally occluding parts of the statue? (such as the inside - you can't see inside it). Even theoretically? Even with a 9x9x9 matrix? Even if you made it very large? And if so, by what chemical or electronics means? 213.246.165.17 (talk) 16:20, 24 July 2014 (UTC)

Steve and Katie, if we back away for a moment, one of the major things in this thought experiment is that it started by assuming that the polarization problem could be fixed from a modular-2 system to a higher dimension of modular arithmetic so that the different layers could all be visible. But of course polarity doesn't work like that. So for starters - if we go back to this assumption: 1) is there a competing technology that lets you go from opaque to transparent? 2) can "that" be filled into a cavity, so that it has some true volume as well? What are our options here, theoretically... (not practically.) Even at 16x16x16 pixels, I haven't seen a demonstration of this (true occlusion), even with terrible optical properties on the logically 'transparent' parts. 213.246.165.17 (talk) 16:02, 24 July 2014 (UTC)

G2 vs Sgr A*

In April this year, the gas cloud G2 was due to collide with the black hole Sgr A* (or at least, when we would see the collision). However, the Sgr A* article has not been updated, and I can't (from a quick search), find anything about it, post-event. Was there anything to report about it? CS Miller (talk) 18:30, 23 July 2014 (UTC)

According to Sagittarius A*#Discovery of G2 gas cloud on an accretion course, observations during the expected time of the perinigricon in March found that G2 remained intact, most likely due to G2 hosting a central star. So it turned out to be kind of a non-event.[38] Red Act (talk) 19:03, 23 July 2014 (UTC)

Thanks Red Act. The paragraph Astronomers from the UCLA Galactic Center Group published observations obtained on March 19 and 20, 2014, concluding that G2 is still intact, in contrast to predictions for a simple gas cloud hypothesis and therefore most likely hosts a central star. does say that. However, the paragaphs before jump between the past and future tense, and reads like it has yet to occur, which is what threw me. Perhaps a copyedit is in order. CS Miller (talk) 19:40, 23 July 2014 (UTC)

Go for it. Red Act (talk) 19:46, 23 July 2014 (UTC)

Carbon auditing

Does carbon auditing, within a system boundary, normally require complicated mathematical calculations? — Preceding unsigned comment added by 176.254.33.42 (talk) 22:13, 23 July 2014 (UTC)

That depends a lot on the system. A coal-powered power station, should be pretty easy - you know the tonnage of coal going in - you know the tonnage of ash and debris coming out the other end - the difference will overwhelmingly be carbon - and you can calculate the amount of CO2 produced very simply.

However, if you wanted to figure out (say) the carbon footprint of a car factory - it's a horrifically complicated calculation because cars are made from a bunch of different materials, there is much processing of those materials and energy is consumed in hundreds of different ways.

It's not likely to be difficult from a strictly mathematical perspective - but the data gathering and the science involved may be a huge undertaking.

SteveBaker (talk) 04:07, 24 July 2014 (UTC)

I agree in concept that no single calculation is terribly complicated from a mathematics point of view, and that it depends a lot on what is being audited. For example, these people [39]. Have done cradle to grave life cycle analysis on the carbon cycles of their energy farm. There are several publications listed at the link above if anyone is interested in seeing how this works in modern practice. To sum up carbon accounting is conceptually relatively simple, and does not intrinsically rely on advanced math. However, in practice, it can become incredibly complicated. SemanticMantis (talk) 14:47, 24 July 2014 (UTC)

Beer cans are easier to squeeze when half frozen. Why?

At room temperature, you can squeeze a can of beer a little. Fully frozen, you can't squeeze them at all. Halfway though, when there's like 50% ice, 50% liquid, squeezing is a lot easier than when it's completely liquid. The biggest component of beer is water which expands while cooling, so why? Joepnl (talk) 23:25, 23 July 2014 (UTC)

It probably has something to do with Ductile–brittle transition temperature (DBTT) –(good luck making sense of the article).   —71.20.250.51 (talk) 00:20, 24 July 2014 (UTC)→[Nevermind]  —I sort of misunderstood the question. Rather than the can itself, it is the change in the resistive force of the contents. Hopefully somebody (else) can provide a better explanation. (?)   —71.20.250.51 (talk) 00:27, 24 July 2014 (UTC)

Well, it's almost certainly something to do with the pressure inside the can right? Water is incompressible either frozen or liquid so my guess is that the answer lies in the gas. The warmer the liquid is, the less gas it can hold, is that right? When you warm up fizzy drink, the gas escapes. So, the most gas is soluble when the liquid is at it's coldest, but not yet completely solid, then obviously mechanical forces of the ice prevent squeezing the can. Does that make sense? Vespine (talk) 01:29, 24 July 2014 (UTC)

I'm trying to find a ref for the claim that cold liquid holds more gas, which does indeed seem to be the case, but the top of my search is "straight dope" which might be mostly correct but not really what I'd call a scholarly source..Vespine (talk) 01:33, 24 July 2014 (UTC)

Wikipedia covers it at Henry's law#Temperature dependence of the Henry constant. Red Act (talk) 02:27, 24 July 2014 (UTC)

You can do an experiment too! Put on your official white lab coat, freeze one can of beer/soda and leave another out of the fridge. When you open the cans, you won't get the same initial "woosh!" of escaping gas from the frozen can - which is because the gas is staying dissolved in the ice and low-temperature water. Also, if you leave a can of soda in a hot car, the base of the can will dimple outwards because the pressure inside the can goes up so high as the CO2 comes out of solution at the higher temperatures (you might not want to test that assertion because the can may actually crack open and fill your car with a foamy, sticky mess). SteveBaker (talk) 04:03, 24 July 2014 (UTC)

Use a can of carbonated water instead of a sugary soda, whether trying either the freezer test or the hot car test. Back to the original question, water expands dramatically when it freezes, but not until then. Chilly liquid water is almost exactly the same volume as warm liquid water. Cullen³²⁸ Let's discuss it 04:52, 24 July 2014 (UTC)

And furthermore, the OP's condition where you have a mix of liquid water and solid ice happens at exactly the freezing point. However, if this is beer then the small amount of alcohol will act as an antifreeze and lower the freezing point of the water...so we're actually likely to be seeing temperatures below zero celcius without yet seeing the large expansion of the water as it changes state - yet still seeing the increased ability to dissolve CO2. So I bet this effect is even more pronounced in beer than in soda. However, soda has a complex mix of ingredients - I have no idea what (if anything) that does to the freezing point - so I could easily be wrong in that guess. But it does mean, for sure, that using canned carbonated water won't demonstrate the effect as well as beer. SteveBaker (talk) 14:43, 24 July 2014 (UTC)

The gas head at the top will also reduce in pressure, by about 1/3% per degree Celsius at room temperature, assuming the gas follows the ideal gas law. ---- CS Miller (talk) 09:07, 24 July 2014 (UTC)

July 24

Question about Hawking's imaginary time

Please don't hesitate to use advanced math in answering this question:

As I understand it, Stephen Hawking thinks the universe is spherically curved in imaginary time.

Would that mean that imaginary time is the radial dimension of the universe's expansion? Why or why not?

If so, would that mean that the universe is expanding slower than light speed? Why or why not?

If the universe is expanding faster than light speed, then why doesn't that make the FRW metric positive-definite?

166.137.101.167 (talk) 02:32, 24 July 2014 (UTC)Collin237

Is this a good image of a pediplain?

I'm determined to find an image for this article, and after researching a bit I discovered that the western Atacama Desert, particularly the Tarapaca region, is home to one of the largest and oldest pediplains on Earth.[40] And so I found [this image], and I'm wondering if anyone with expertise or familiarity with the region can confirm that this is in fact (part of) a pediplain. And furthermore, is it a good enough representation to include in the page? If so, I can modify the image with some labels to make it clearer. = NV1982 ^(talk) 06:16, 24 July 2014 (UTC)

Interesting! It looks like you've done your homework. I've read through your links, and it seems right to me... but I'm no geographer or geologist. I suggest (barring any credible, referenced, objections here in the next few days) that you be WP:BOLD and add the image to the article :) SemanticMantis (talk) 14:50, 24 July 2014 (UTC)

Origin of body heat when cycling

When I cycle, which are the main contributors to (over) heating my body - muscles in my legs, heart, diaphragm and intercostal muscles? --129.215.47.59 (talk) 10:20, 24 July 2014 (UTC)

That is waste heat generated when muscles convert chemical energy into kinetic energy. StuRat (talk) 15:16, 24 July 2014 (UTC)

Alternate Fuel and Car Technology

Hi wikipedia, I dont have a great article to publish but certainly a new idea which i would like to share it with you. Recently i have been thinking about powering cars with wind energy ,can i do so? i have a basic idea not exactly a technical one , so need help hope so ull reply . — Preceding unsigned comment added by Manojb95 (talk • contribs) 12:05, 24 July 2014 (UTC)

Lots of obvious problems with that. Your best bet is to charge batteries using a turbine, which is already done. Any ideas about sails and turbines mounted on cars are, sadly, not feasible. Zzubnik (talk) 12:25, 24 July 2014 (UTC)

This is a much underappreciated aspect of history - see land sailing, ice boat, ice yachting. We've seen a thousand film images of Conestogas but anyone ever see a "wind wagon" in film (??!) I remember reading something about ice boats having held the land speed record on Lake Michigan for a time but can't find it now. (maybe a logician objected?) Wnt (talk) 12:50, 24 July 2014 (UTC)

These old Chinese devices are pretty close to a wind-propelled wagon Wheelbarrow#Chinese_sailing_carriage. Google /Chinese wheelbarrow sail/ for lots of cool pics and articles. SemanticMantis (talk) 13:17, 24 July 2014 (UTC)

Wind-powered vehicle has examples of the turbine type. Katie R (talk) 13:25, 24 July 2014 (UTC)

We should probably mention some of the problems that make it not feasible:

1) You can't go faster than the wind in a vehicle powered solely by the wind. In most places, the wind doesn't go very fast, most of the time, so your car would be slow. When there is no wind, your car wouldn't move at all.

2) The wind often goes in the wrong direction. While sailboats can go in the opposite direction as the wind, via tacking, this involves sailing in a zigzag pattern that's not practical for land vehicles following roads. Out on an open desert, it's a bit more practical.

And, in case you are thinking you could power a car by conventional means, and put up a windmill to capture wind energy too, that won't work, since the drag from the windmill will slow the car down more than the electricity generated would speed it up.

So, I agree that the best way to power a car by wind energy is to use a windmill to charge batteries for an electric car. However, for a car that gets much use, if the windmill is only set to charge the batteries and nothing else, the best option is to charge the batteries outside the car, and just swap those in for the discharged batteries in the car whenever you leave home. Alternatively, if wind power is used to generate electricity on the grid, then you can just use a standard plug-in electric vehicle. (In many places you can sell your unused wind energy back to the power company using the grid.)

One other possible use of wind energy for powering a car is when parked away from home. You could conceivable have a windmill that deploys above the car to trickle charge it while parked. However, this would provide rather minimal power, so would only be practical if parked for long periods in windy areas, with only short drives. Also, high winds might tip the car over, necessitating the use of outriggers (I see our article is just on boats, don't we have one for outriggers on cranes, etc. ?), which would add to the weight of the vehicle. StuRat (talk) 14:04, 24 July 2014 (UTC)

I agree that these vehicles aren't practical for everyday use. However, your first claim is wrong. Blackbird (land yacht) can go upwind and downwind faster than the wind speed and doesn't need to tack. Katie R (talk) 14:21, 24 July 2014 (UTC)

(EC) Your comment 1 seems very confusing or inadequately explained as our article sailing faster than the wind (and perhaps vehicle) will indicate. Nil Einne (talk) 14:23, 24 July 2014 (UTC)

The key to understanding the concept is that by using a turbine coupled to the wheels, it can use the speed between the air and the ground, not just the relative speed between the air and the craft. Katie R (talk) 14:26, 24 July 2014 (UTC)

Note that I'm not just thinking of Blackbird concept but the general concept of sailing faster than the wind. StuRat's comment 2 mentioned the issues tacking etc poses for road based vehicles. But comment 1 didn't say anything about that nor did it refer solely to sailing dead downwind. So comment 1 seems to ignore the more general idea where you can use tacking or other methods to achieve a VMG higher than the windspeed particularly on ice boats (which Wnt already mentioned) and unlike Blackbird, I don't think is something only recently demonstrated (if you didn't believe the theoretical calculations), even though StuRat's comment itself could be taken to imply this isn't possible. These may not be practical for most land based vehicles but again, the comment was phrased very generally. So I'm not sure making the claim as StuRat did without additional explaination of what they were referring to, or at least a link to our article (which I found in about 3 seconds), helps the OP much. Nil Einne (talk) 14:44, 24 July 2014 (UTC)

Aside from the physics of the thing, consider the economics. A typical car engine puts out something of the order of 100kWatts. According to The American Wind Energy Association a 1kWatt turbine costs between $4000 and $9000 (already way too expensive to put onto a car!) and a 100kWatt turbine costs $350,000. So right there, you know that you can't bolt a wind turbine to a car and get free energy. However, since you aren't driving your car 24 hours a day - and the wind might maybe blow 24 hours a day (in a good location) - if you restricted yourself to driving for at most one hour per day, then you could charge the batteries on an electric car with a mere 4kWatt generator. Sadly, that's still going to cost you more than your car...but why bolt the thing to your car? Why not use it to charge the batteries and leave it behind when you drive off? What this leads you to is that electric cars are a good idea...and that using wind energy to make electricity is a good idea. These are completely separate concepts though...linking them together and saying "Let's run a car on wind" is an unnecessary (and exceedingly difficult) linkage! Why have your expensive windmill only work while you're driving your car? Why not use it to power your refrigerator instead?

Taking it one step further - the larger a windmill is, the more efficient it becomes. That's why the wind energy folks use windmills with blades the size of a 747's wing. So having each person who drives an electric car spend all that money on a 4kW windmill is silly. You need to fund your share of a megawatt windmill and share it with everyone else...or, in other words, buy your electricity from a wind-energy company and run an electric car.

What most concerns me is that you're probably thinking "Wow! When I drive my car, and stick my hand out of the window, there's a heck of a lot of wind! Why can't I capture some of that to drive the car?" - and that's a fatally flawed argument. The problem is that windmills cause drag...in fact, that's what their function is - to cause as much drag as possible, slowing down the airflow and stealing energy from it. So if you could bolt a small windmill onto your regular car, it would increase the drag on the car such as to increase fuel consumption by an amount of energy that would most certainly be considerably more than the windmill would generate. That's 100% certain - and it doesn't depend on how clever your design for the windmill is - or how you use it's energy. The laws of thermodynamics guarantee that this approach won't work...no matter how clever you are!

The only thing that might work would be to have a windmill that popped up out of the roof of your car when you stepped on the brakes! The windmill would slow the car down AND generate energy. This might, somehow be a seemingly good idea (I doubt it!) - but cars that recover energy from the braking systems ("regenerative braking") already exist - the Prius does that exact thing - except that it turns the electric motors that drive the wheels into generators when you step on the brakes - and that requires no new mechanical systems - just $10 worth of electronics. So if you already have an electric car, that's a vastly cheaper, easier, more efficient approach than trying to capture the energy from the air flowing over the car.

So, sadly, this idea is a non-starter. Not going to work!

SteveBaker (talk) 14:32, 24 July 2014 (UTC)