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April 15

Caustic size variation with temperature

I've noticed that you can see how cold a swimming pool is when it is lit by sun and the water is not still by simply noting the pattern of light dappling the bottom. Cold water has smaller sharper looking caustic patterns while warm water has large soft and slowly moving caustic patterns. Why? -Craig Pemberton 02:09, 15 April 2010 (UTC)

It may not be the overall temp that's directly important, but rather the range of temperature variations within the pool, as each temperature change has an associated change in density, and thus a refraction occurs at the boundary layer. Perhaps a pool which is overall colder but also in sunlight tends to have more temperature variations, and thus more refraction ? StuRat (talk) 02:14, 15 April 2010 (UTC)

To test this I drew a scalding hot bath in a cold tub. The caustics were relatively small. -Craig Pemberton 00:20, 19 April 2010 (UTC)

ISS EVA Capabilities

Hey everyone and thanks in advance for reviewing my question. The bottom line of my question is: does the staff stationed at the International Space Station have the ability to do EVAs (spacewalks) when there is no visiting mission (NASA Space Shuttle or otherwise). In response to the current valve failure in the nitrogen/ammonia tank assemblies, a lot of talk is heard about whether an EVA could be done during this shuttle mission or the next, however I hear no talk about whether the station crew could do a spacewalk during the interim. Obviously, it would be preferable to do spacewalks during visiting Shuttle missions, because the astronauts going up have the ability to train for the exact procedure in advance, but in a more urgent situation, is it possible (with standard equipment kept on the Station, etc.) for the station crew to do a spacewalk during a time when there is no docked mission vehicle? --Nick—^Contact/_Contribs 04:25, 15 April 2010 (UTC)

Sure, They've got both the Quest Joint Airlock and the Pirs docking compartment, though the later is apparently only compatible with Russian suits.

This has been done a number of times. Check out the List of spacewalks since 2000. I believe that all the space walks where "Expedition [number]" is listed as the "Space craft" were based from the space station when no shuttle was docked. (This list is not terribly clear on this point.) APL (talk) 05:15, 15 April 2010 (UTC)

I notice the quest airlock says it allows both kinds of suits, however the Pirs only allows the russian Orlan suits. What is the factor that prevents a US suit being used in the Pirs airlock? Some sort of coupling? I didn't think you had to be coupled during EVA. Vespine (talk) 06:02, 15 April 2010 (UTC)

I'm guessing - but I know that you have to pre-breathe pure oxygen for quite a while before you go outside in order to purge nitrogen from your system to avoid getting "the bends" in the lower pressures used in the spacesuit. That takes a long time - and it has to be done in the airlock because the pressures have to be gradually reduced while you do it. You wouldn't want to be using your limited supply of suit oxygen for that - so if the issue is one of suit couplings, that would explain the problem. SteveBaker (talk) 13:26, 15 April 2010 (UTC)

Car trick

I was looking at the following video: http://www.youtube.com/watch?v=qKxgNOR5QnY&feature=related, and I had some questions about the physics. First, how stable is the car in this situation? It seems precariously close to falling over, but often looks can be decieving. I would imagine that, for the trick to have any reasonable chance of success, the car has to be somewhat stable. But from what I can see, the center of mass seems to be nearly over the the wheel. Do you think weights were added to the left side of the car to make it appear less stable than it actually is?

Second, would it be possible to use the gas in this situation, what with the wheel not being flat on the ground? Thanks 173.179.59.66 (talk) 09:34, 15 April 2010 (UTC)

Oh, and how do you think they would return the car back to its original position? I would think a sharp right turn would do the trick, but is turning right really and option when only two wheels are on the ground? 173.179.59.66 (talk) 09:36, 15 April 2010 (UTC)

Here's the Wikipedia article on it Ski (driving stunt). 194.221.133.226 (talk) 10:03, 15 April 2010 (UTC)

though i'm not convinced by the article - my understanding was that you needed specialist work done to the Axles as otherwise they basically just snapped...That said maybe what I head was a load of cr@p. 194.221.133.226 (talk) 10:05, 15 April 2010 (UTC)

A lot depends on the weight of the vehicle. Something as heavy as the vehicle in the video might well need stronger axles - but I've seen the stunt done with lightweight vehicles that have definitely not been modified ([1], [2], [3], [4], etc). The difficulty lies in getting the vehicle in that position in the first place - you have to hit the ramp at a fairly exact speed to get it to that position without tipping over. However, once it's up there (I'm told), keeping it there is relatively easy - and the larger the vehicle, the easier that is. This is one of the more easily done car stunts - you just have to practice the "getting it up to that position without rolling it over" part. The moment of inertia of a car is huge - it responds fairly sluggishly and you have plenty of time to react to keep it up on two wheels. Steering is done much like on a bicycle...and again, I'm told that isn't difficult. SteveBaker (talk) 13:21, 15 April 2010 (UTC)

as in you haven't ridden a bycycle SteveBaker or as in the steering isn't difficult (much like riding a bike isn't). 194.221.133.226 (talk) 14:47, 15 April 2010 (UTC)

Russ Swift is a well-known stunt driver who regularly appears on Top Gear episodes doing stunts such as these (amongst many others). He also showed Jeremy Clarkson how to do the ski in one of Clarkson's motoring specials. Zunaid 14:55, 15 April 2010 (UTC)

The car in that trick is about as stable as a bicycle. In both cases keeping balance is by a combination of leaning one's body and steering. Having power steering may help. It looks like the stuntmen are not too stressed to wave to the onlookers. I don't think any weights were added to the car. Higher air pressure in the tires might help. The car in the video is probably not the first one in which the driver has tried the trick because it looks undamaged. It is unsurprising to see the trick done by arabs with enough disposable income to play with new vehicles, insignificant fuel price and wide open flat roads without much traffic regulation. Ancestral skill at balancing on lurching camels may help too.
@Second, yes the driver uses the engine to keep the car moving because otherwise it would slow to a stop and become harder to keep balanced when one loses the gyroscopic effect of the rotating wheels. Like on a bicycle. I think the car drivetrain needs to have an LSD or 4WD to sustain the trick.
@Last I'm sure it is easier to come down with a bump than it is to go up. Getting up seems extra risky when done without a ramp but I never saw an example of a car overtoppling on youtube. Cuddlyable3 (talk) 16:47, 15 April 2010 (UTC)

One of the finest articles on Wikipedia is Bicycle and motorcycle dynamics - it says that the idea that some gyroscopic effect is responsible for the stability of a bicycle is discredited. It's all to do with the angle of the front forks. However, the geometry of the steering mechanism of most cars confers similar stability in this case. SteveBaker (talk) 23:29, 15 April 2010 (UTC)

Thanks for the quick replies! Quick question about the stability though. On a bike I'm abe to stay upright by shifting my weight. If the car were to start falling one way or another, how could the driver compensate?173.179.59.66 (talk) 05:22, 16 April 2010 (UTC)

By turning the wheel left/right which will move the car in the (hopefully) opposite direction in which it is falling. Ariel. (talk) 12:48, 16 April 2010 (UTC)

The driver will shift his body weight too. I don't think anyone does the trick while wearing a seat belt. Cuddlyable3 (talk) 23:13, 16 April 2010 (UTC)

Wolverine vs Honey Badger

In a hypothetical fight to the finish, which one would most likely be left standing? Exxolon (talk) 10:02, 15 April 2010 (UTC)

Quite clearly the wolverine. The wolverine often takes prey such as reindeer calves. While both are omnivores, the wolverine can grow heavier than 20-23kgs, whereas a honey badger will not become much more than 14kg (this according to their respective articles). Badgers in general will far more often dine on animals lesser in size than themselves. 88.90.16.251 (talk) 12:20, 15 April 2010 (UTC)

Are you sure? I've seen a video of a honey badger seeing off a lion. Zzubnik (talk) —Preceding undated comment added 13:30, 15 April 2010 (UTC).

Lions tend to be non-confrontional, and regularly back down from fights with smaller animals. Hyena are often observed chasing lions off. Lions would win if they fought such an animal, but they tend to not want to. --Jayron32 14:58, 15 April 2010 (UTC)

Well, not to be overly pedantic or anything, but if the lion backs off, the lion loses the fight, right? He's disqualified himself out of sheer cowardice. Comet Tuttle (talk) 18:17, 15 April 2010 (UTC)

I think if the lion and the honey badger were locked in a cage, and had to fight to the death, the lion could tear it to shreds. If forced to fight, the lion wins. If it doesn't have to fight, however, why bother? --Jayron32 18:54, 15 April 2010 (UTC)

Predatory animals don't generally like to engage in fights against opponents where there is a non-insignificant chance of injury. Injuries, even small ones, tend to add up over the years, you see - and affect the predator's ability to hunt. Impaired hunting ability = death in the cold, hard, brutal indifference of nature. So they will only tend to go after what they consider to be 'soft targets' - unless the situation is extremely dire. --Kurt Shaped Box (talk) 20:59, 15 April 2010 (UTC)

Indeed in such circumstances both win. The larger animal who could have won the fight but would have suffered unnecessary injury doesn't suffer that injury and the smaller animal who would have lost the fight lives another day. One might argue similar things for most human fights where generally the outcome for both is better if they just don't fight. It's usually unfair to say the person who backed down 'lost' just because they avoided a silly fight which would have benefited no one. Nil Einne (talk) 07:42, 16 April 2010 (UTC)

now result

i am very angry to use this web page but could not have any result pattaining to my search —Preceding unsigned comment added by 41.202.199.4 (talk) 11:36, 15 April 2010 (UTC)

If you can let us know what you were searching for, we might be able to help you find it. Karenjc 12:22, 15 April 2010 (UTC)

A little atitude adjustment is likely in order as well. Dauto (talk) 14:19, 15 April 2010 (UTC)

I was assuming that, since the OP's first language doesn't seem to be English and his IP address geolocates to Cameroon, what he meant could have been closer to "I feel bad about coming here asking, but I can't find what I need by searching". Karenjc 14:36, 15 April 2010 (UTC)

Also a little spelling adjustment?--79.76.228.211 (talk) 14:59, 15 April 2010 (UTC)

Could you be looking for something called "NOW", such as the National Organization for Women ? StuRat (talk) 14:21, 15 April 2010 (UTC)

What do these symptoms lead to?

I have been given a fake "patient" with the following symptoms: fever, dizziness, vomiting and diarrhea, a diffuse maculopapular rash on all limbs, puffy edema of the face and extremities, and raised temperature, pulse, blood pressure, and respiration. What do these symptoms lead to? At first, I thought it was meningitis, but he doesn't have a stiff neck ... I'm completely lost.

Also, we found through Gram-Staining that he has numerous PMNs (polymorphonuclear cells) and many gram-positive cocci as single cells, in pairs, and in clusters. A blood test was negative. —Preceding unsigned comment added by 69.16.95.123 (talk) 11:39, 15 April 2010 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.

Ah, come on, he has "attempted to solve the problem himself", and is stumped. What more can we expect him to do, other than looking through some medical reference book or browsing through random wikipedia articles or something. It seems like an appropriate step to ask for help on-line. I am a bit worried about giving medical advice though, even for a "fake patient". I'll start a thread on the talk page. Buddy432 (talk) 15:00, 15 April 2010 (UTC)

Here's the thread I started. Buddy432 (talk) 15:08, 15 April 2010 (UTC)

(from talk page) Ask, Were thy on any medication prior to admittance? I'm thinking along the lines of discounting any adverse drug reaction, especially the rarer ones caused by to or more drugs. --Aspro (talk) 15:16, 15 April 2010 (UTC) —Preceding unsigned comment added by Buddy432 (talk • contribs)

Has Dr House told you what he thinks yet? He is usually wrong on the first couple of tries. Googlemeister (talk) 16:03, 15 April 2010 (UTC)

... and don't forget that it's never lupus - except when it is. Gandalf61 (talk) 16:38, 15 April 2010 (UTC)

I'd not discount meningitis just on the absence of one symptom. It's too severe an infection to discount like that. Also, there are symptom sorters available online (yourdiagnosis.com) or in written form. Have you also ruled out measles or rubella?

Your first paragraph includes symptoms that could result from a range of diseases, including infections, vasculitis, and systemic inflammatory processes. However the presence of numerous gram positive cocci is a giveaway. This is almost certainly either Streptococcus or Staphylococcus. The clusters are more suggestive of Staphylococcus; the most likely cause is Staphylococcus aureus septicaemia. Axl ¤ [Talk] 20:22, 15 April 2010 (UTC)

You make a very good point; the previous post makes a very good point also, about not discounting meningitis just on the absence of one symptom. It goes therefore, without saying that ”Time is of the essence”, and this is not the time to discuss the evils of over proscribing antibiotics. BUT what does one do (now, at this very moment)? The word 'many', as in “many gram-positive cocci as single cells, in pairs, and in clusters” is not a truly objective, any more than anything else said - (pictures would have been nice). So does one give a gram antibiotic? Time may be running out.--Aspro (talk) 21:19, 15 April 2010 (UTC)

Well, I thought that the OP was asking for help on the (fake) diagnosis. So you want to know about treatment? Axl ¤ [Talk] 07:45, 16 April 2010 (UTC)

So taking into account Axl's putative diagnosis of Staphylococcus aureus septicaemia, test for methicillin resistance in case this is MRSA: if so, find an antibiotic that works and start therapy pronto! --TammyMoet (talk) 21:00, 16 April 2010 (UTC)

But what about the unlikely chance that this is a real patient, or that these exact symptoms will be used for a real diagnosis in the future? ~AH1^(TCU) 16:20, 17 April 2010 (UTC)

DNA Bases

Why are the bases in DNA/RNA said to be hydrophobic if they can form hydrogen bonds? —Preceding unsigned comment added by 67.177.181.221 (talk) 14:06, 15 April 2010 (UTC)

Are they hydrophobic? Do you have a source for that. Looking at the structure, I would think they would be fairly hydrophilic; their presence in the cytoplasm (which is mostly water) would indicate that they aren't. Indeed, if they were hydrophobic, I would expect them to cluster or agglomerate in such a way as to make them not work as they do; the fact that they exist free-floating in the cyctoplasm indicates to me that they aren't hydrophobic. I could be proven wrong, but where is the assertion that they are? --Jayron32 14:56, 15 April 2010 (UTC)

When 67.177.181.221 refers to the hydrophobicity of nucleotide bases, that may be a reference to the sides of the base, not the edges. As the bases are aromatic, the flat bits (the top and bottom) are covered by a poorly polarizable (at least in the direction normal to the plane of the rings) delocalized electron cloud. While pi-pi stacking interactions readily occur, all of the hydrogen bonding and polar interactions happen "edge on" in the same plane as the rings. -- 174.24.208.192 (talk) 07:23, 17 April 2010 (UTC)

Electrolysis

I understand the concept of electrolysis, but what does it mean to apply a voltage? Say a cell that has a net voltage of -2V as indicated by potentiometer (and since -2 is negative, the redox reaction is nonspontaneous.) My textbook says you need to apply -2V to drive this reaction. But shouldn't you apply +2V? I totally don't understand the concept of applying a voltage. —Preceding unsigned comment added by 142.58.43.216 (talk) 16:31, 15 April 2010 (UTC)

Some people like to think of electricity in terms of the Hydraulic analogy where voltage (or "potential difference") is compared to pressure of a fluid. One connects anything that might pass current to a voltage source (such as a battery) by two wires, just like in the analogy one connects to a pump by two pipes for forward and return flows. The negative terminal of a voltage source is the one where there is a surplus of electrons. Cuddlyable3 (talk) 17:02, 15 April 2010 (UTC)

Yea, the sign doesn't really matter. 2V just refers to the differential between the two wires. Depending on which wire is positively charged and which is negatively charged, the electrons will flow one way or the other, and this is what the + and - show. However, the anode and cathode should be made of different materials for electrolysis, so you do need to know which gets connected to the positive and negative terminals. StuRat (talk) 18:42, 15 April 2010 (UTC)

No, the materials need to be of different materials if you are making a galvanic cell. For an electrolytic cell, just about any inert conductor will do fine. They can be the same material. --Jayron32 19:08, 15 April 2010 (UTC)

My question is still not answered. Why does it not matter if you apply a + or - voltage? In electrolysis, it should matter because the natural voltage between two nonspontaneous redox reactions should be negative. My incomplete understanding of this is making it hard for me to further understand the basics of voltammetry. —Preceding unsigned comment added by 142.58.43.94 (talk) 19:31, 15 April 2010 (UTC)

In electrolysis, the two electrodes are in the same solution. So it doesn't matter whether the electrode in your left hand has the higher voltage or the one in your right one does. The process will happen the same either way; the only difference will be at which electrode the oxidation process goes on and at which one the reduction process goes on. However, the sign of the voltage is merely directional. It only tells you whether electrons are flowing in or out of that particular electrode. The actual process will occur regardless of the direction; the only difference will be which half-reaction will take place at which electrode. --Jayron32 19:56, 15 April 2010 (UTC)

(after edit conflict) ::::A voltage is just a potential difference between terminals. Whether you call it +2V or -2V depends on how you measure it. As mentioned above, for electroysis, the + side of your voltage source goes to the anode, and the - to the cathode. The anode is +2V with respect to the cathode, or you could say that the cathode is -2V with respect to the anode. If anode and cathode are the same material, then it doesn't matter which is which, but the direction of the electrolytic separation will depend on the direction of the current, and this depends on which side is positive and which side is negative. Traditionally, current flows from + to - but negatively charged ions will flow the other way. Dbfirs 20:05, 15 April 2010 (UTC)

sodium carbonate

does sodium carbonate (soda ash) degrade when exposed to air? or does it remain corrosive? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 18:41, 15 April 2010 (UTC)

It depends on which sodium carbonate you mean. Sodium carbonate exists naturally in several different hydrated forms, see Sodium_carbonate#Occurrence. I am pretty sure they are all fairly stable for any reasonable amount of time. Pure, unhydrated sodium carbonate is likely somewhat hygroscopic, so you can likely generate one of the hydrate forms if you leave it out on a humid day for some time. And acid will tend to degrade the sodium carbonate first to sodium bicarbonate then to carbonic acid; the latter of which is metastable and decays quickly to carbon dioxide and water. But if kept dry and in a sealed container, I think that sodium carbonate can keep indefinately. --Jayron32 18:59, 15 April 2010 (UTC)

im talking about the kind you buy in the store for cleaning. its not in a sealed container but rather in a pile on the counter —Preceding unsigned comment added by Jonny12350 (talk • contribs) 19:45, 15 April 2010 (UTC)

In that case, its cleaning properties are largely because it is abrasive and not corrosive. In other words, its gritty, and so tends to break dirt and stains up into smaller bits to make them easier to wash away. It is slightly alkali in nature, so it will saponify any oil-based dirt, to a small extent, which also helps. Due to the ion exchange effect, it can, like all ionic salts, speed the corrosion (rusting) of iron much like ordinary table salt (sodium chloride) does, so I would rinse it off any metal surfaces you cleaned with it; but by itself it isn't usually very corrosive. Douse with water and follow with several wipes with a damp sponge, and your metal surfaces should be fine. --Jayron32 20:04, 15 April 2010 (UTC)

It may react with atmospheric carbon dioxide to form sodium bicarbonate, but that shouldn't affect its cleaning or water softening abilities. --98.221.179.18 (talk) 00:37, 17 April 2010 (UTC)

April 16

The mass of something 1836 times smaller than you?

An electron is only 1,1836 the mass of a proton. If your mass was 50 kilograms, what would be the mass of something 1836 times smaller than you? Try it the other way. What would be the mass of something 1836 times larger than you? —Preceding unsigned comment added by BlackBerryStromGuy (talk • contribs) 00:51, 16 April 2010 (UTC)

Not sure what you're asking here, but this appears to be simple arithmetic. If you weigh 50kg something that's 1836 times smaller than that weighs 50/1836 kg (about 27g or call it give or take 1Ounce. Something 1836 times 50kg is 50 * 1836 kg or about 90 tons. Call it about 19 elephants. Tonywalton ^Talk 01:07, 16 April 2010 (UTC)

This reads like a homework question, yet it makes no sense as a homework question to me. Why did you need to know this? Vimescarrot (talk) 10:44, 16 April 2010 (UTC)

Neutrons have slightly more mass than protons and I have plenty of them in me, how is it on your planet? Cuddlyable3 (talk) 12:33, 16 April 2010 (UTC)

I simplified the title for reference. Cuddlyable3 (talk) 19:30, 16 April 2010 (UTC)

I think the OP is asking for the name of an object that is either 1836 times smaller or larger in terms of mass than a 50-kg person. ~AH1^(TCU) 16:16, 17 April 2010 (UTC)

Internet searches for non-linear notations

Please see Wikipedia:Reference desk/Computing#Internet searches for non-linear notations. -- Wavelength (talk) 01:21, 16 April 2010 (UTC)

Icelandic volcano and air travel.

So - just how long could the volcano in iceland keep aircraft from flying over the UK? Some sources say that the wind could change direction - like that would solve the problem...but couldn't this think keep on belching dust for a very long time? Just how long could it keep going? Days? Weeks? Months? Years? SteveBaker (talk) 02:21, 16 April 2010 (UTC)

This article quotes a volcanologist at the University of Edinburgh as saying that the eruption could last years. As for disruption of air traffic, it will very much depend on the direction of the winds aloft. After British Airways Flight 9 and KLM Flight 867, the aviation industry is very concerned about flight though volcanic ash clouds. -- Flyguy649 ^talk 02:38, 16 April 2010 (UTC)

If it keeps going for years - the wind is going to cause this kind of chaos several times a month for all that time? That would be kinda annoying! SteveBaker (talk) 02:54, 16 April 2010 (UTC)

Yup. Rio de Janiero might become a big hub for Europe-North America air traffic! -- Flyguy649 ^talk 02:56, 16 April 2010 (UTC)

And US-Europe cruiseships may see a revival. caknuck _° needs to be running more often 06:21, 16 April 2010 (UTC)

(Western/Nothern) Europe is perhaps somewhat fortunate that they have decent high speed rail for intra Europe travel which may get a further boost if this disruption continues. BTW, [5] suggests that repeated disruptions are definitely possible. Incidentally, as someone who just purchased something from Germany and paid a lot for shipping to because of $#(*&%!* Deutsche Post/DHL's we don't price by weight for packets policy the disruption is rather annoying. Nil Einne (talk) 07:23, 16 April 2010 (UTC)

Ironically I just realised the German airspace wasn't closed at the time I wrote my message above although it is now. Of course since the packet was only sent on Friday it probably will still be in the system in Germany somewhere and may not have really been affected yet. Nil Einne (talk) 15:53, 17 April 2010 (UTC)

Epic: "Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped." --Sean 16:52, 16 April 2010 (UTC)

Cool animation of the ash plume from the ESA. -- Flyguy649 ^talk 09:52, 16 April 2010 (UTC) We can survive cancelled commercial flights for a while but there are other emergency aviation needs such as air ambulances, mountain rescue and forest firefighting. Would a battery powered electric helicopter be a feasible solution at this time? Cuddlyable3 (talk) 12:27, 16 April 2010 (UTC)

Battery powered helicopters can barely support their own weight. But you could use a helicopter with internal combustion and a filter (like a car engine basically), instead of a jet engine or turbine. And I think most non-military helicopters are internal combustion. Also, fly low, under the plume. Ariel. (talk) 12:51, 16 April 2010 (UTC)

Au contraire. See the "Hexacopter," which can carry itself plus a substantial payload. Would the size/mass problem that defeated Langley prevent its being scaled up? Edison (talk) 20:09, 16 April 2010 (UTC)

It weighs 1.2Kg, and can carry 1Kg, with a flight time of a couple of minutes. 36 minutes with no payload. In contrast a typical gas powered helicopter also has a payload of about it's own weight - but it can do it for hours. Ariel. (talk) 01:49, 18 April 2010 (UTC)

Because the eruption was largely unexpected, the safest course of action in the short-term was to simply cancel all flights in affected areas and put up with the inconvenience and economic losses. If the hazardous conditions exist for a few more days, flight plans will be developed to avoid the affected areas. If conditions last for a few more weeks, safety assessments will take place and flight procedures will be developed that fly in the affected areas but minimize the risk. If the hazardous conditions really do last "several years", then we will have time to develop engineering fixes to the flight control electronics, engine intakes, and so on, to accomodate the non-ideal conditions and safely fly through zones with large amounts of volcanic ash. This is really a matter of estimating how much effort should go into developing solutions for a problem which might be temporary anyway. If global dispersion of volcanic ash becomes the most serious impediment to air travel over the next several decades, we will see engineers developing revolutionary new kinds of aircraft that are impervious to ash plumes - but that would only be worthwhile if the consequences of volcanic eruptions are huge. Nimur (talk) 15:35, 16 April 2010 (UTC)

Engineering fixes seem difficult at best. Aircraft that have flown through ash plumes in the past had all of the paint scoured off the plane and the windows 'sandblasted' to the point where it was impossible to see out! The very nature of jet engines is that:

• They take in a lot of air at high speeds...filtering that air is not a possibility.
• They burn fuel at temperatures high enough to melt the tiny rock fragments in the ash and turn it into the sticky glassy substance that then coats the internal parts.
• That the fuel burns at a temperature that's high enough to melt the engine parts themselves if there isn't a cooling airflow ducted in through narrow holes that get blocked by the ash.

It's not going to be easy (and perhaps not even possible) to fix those things. SteveBaker (talk) 18:14, 16 April 2010 (UTC)

Rocket planes wouldn't suffer those engine problems, because they have no air intake. Abrasion could be a problem, but I feel confident that it could be solved. SpaceShipTwo is already well into the design phase - this is not an impossible idea! But these rocket-powered aircraft are not cost-competitve with conventional aircraft - so rocket planes could only become mainstream if conventional aircraft become totally inoperable over a long enough period of time to affect airline company technology strategies. Nimur (talk) 14:37, 18 April 2010 (UTC)

Why couldn't air routes be lowered to fly under the plume? (High mountain areas excepted). Certainly it would be louder for those on the ground. How much would fuel consumption go up at say 10,000 feet (3000 meters) rather than 30,000 feet (9100 meters) or whatever is the favorite altitude for passenger jets? Edison (talk) 20:11, 16 April 2010 (UTC)

Because a) debris is constantly precipitating out of the debris cloud and b) this would require constant monitoring of the ash cloud ceiling (which can vary greatly locally) over an area of tens of thousands km². Better to go around than under. caknuck _° needs to be running more often 22:16, 16 April 2010 (UTC)

After the eruption of Krakatoa, there were no airplane flights for 20 years!! Edison (talk) 03:57, 17 April 2010 (UTC)

Soviet historians strongly disagree! Nimur (talk) 18:04, 18 April 2010 (UTC)

As the eruption continues, the ash plume could drift west over the North Atlantic, cooling the region and possibly setting off the negative phase of the Atlantic Multidecadal Oscillation. Any long-term effects on climate are expected to be slight, but the eruption contains both SO₂, which could cool the ash-affected regions of Western Europe while increasing severe weather in the region and producing acid rain, as well as water vapor which would produce a net contribution to the warming of the globe as it is emitted into the stratosphere where it has the biggest effect. Also, the volcano is likely to trigger a second eruption at Katla, which would prolong the ash plume even further and melt more of the glacier in Iceland which would melt into the sea, flooding more villages and having a slight effect on global current sea level rise. ~AH1^(TCU) 16:09, 17 April 2010 (UTC)

Our article says no long term climate effects are expected yet but they could still occur. Nil Einne (talk) 19:22, 17 April 2010 (UTC)

Some interesting facts from our article talk page.

1) It seems it isn't true all aeroplanes are grounded. Rather only IFR are forbidden. Many places still allow VFR. Of course all commercial flights and large planes use IFR so they're all affected. And VFR implies you have to stay fairly low and have to be able to actually see where the aircraft is going so if the situation is so bad you can't see, you can't fly VFR.

2) One Russian plane did try this 'fly low' thing. However it's not clear how well planned this was since they ran out of fuel and had to divert to Vienna (original destination had been Rimini, Italy). In any case, even though they are supposed to have flown below the ash cloud, there are still calls for very rigorous inspection of the plane.

Nil Einne (talk) 19:22, 17 April 2010 (UTC)

Why not use piston engine powered propellor planes? Count Iblis (talk) 02:22, 18 April 2010 (UTC)

Black lights, wattage, and wave lengths

I have some glow in the dark powder pigment, specifically this that I use sometimes, and have been using a 75 watt GE black light bulb to charge it. I also have a 3W led UV light. The led operates at 395-400 nm wavelength, I think the 75W is at 365. Any ideas about the differences is the effectiveness of charging the powder? Using the flashlight is vastly preferable but not at a huge sacrifice to a brightness from the powder. Beach drifter (talk) 03:20, 16 April 2010 (UTC)

You need a certain wavelength to charge it. A longer wavelength will not charge it at all, and a shorter one just wastes energy. Once you have that wavelength, the brighter the light the faster it will charge (more or less). To find out how bright the bulb is, in theory you want the lumen or candela, but those are adjusted to human vision, and UV does not rate. Electrical watts tells you very little since you don't know how efficient the bulb is (unless they are both the same type, you did not specify). Confusingly, Radiant flux is also measured in watts. So are those electrical (input) watts or radiant (output) watts? Note: the powder could be a mix, and might have multiple desired wavelengths, but I think pure green isn't a mix. Ariel. (talk) 04:01, 16 April 2010 (UTC)

I'm fairly certain the powder is not a mix, it is very strong, pretty awesome stuff. The 75W bulb is an incandescent type that you can get at Walmart. The down side is that it gets very very hot and when camping requires a dc to ac converter and a car. Beach drifter (talk) 04:12, 16 April 2010 (UTC)

I think that Incandescent UV bulbs are ordinary bulbs with filters that remove visible light. The UV efficiency is probably horrible (but I don't have numbers). So despite being 75 watts little UV is made. But probably more than 3 watts worth. Can you do a test, just because I'm curious? Try to charge the powder with a regular 75 watt bulb. Anyway, what I would suggest for you is a 12 volt portable fluorescent lamp with a built in battery. Car mechanics use them, so it should not be hard to find. Ariel. (talk) 21:32, 16 April 2010 (UTC)

Palatine uvula

I read the article on this but didn't find the answer I was looking for. My query is: other than humans, do other animals have a uvula? If so, what it it used for since humans use it for language? —Preceding unsigned comment added by 99.250.117.26 (talk) 04:21, 16 April 2010 (UTC)

It is adapted by humans for use in language. Its other purpose is to close off the nasal sinuses from the throat, to prevent food from getting into your sinuses when you swallow. See also Epiglottis for a similar flap covering the trachea. --Jayron32 04:29, 16 April 2010 (UTC)

How does the uvula, which exists in the oropharynx, prevent food from getting into the sinuses, which communicate with the nasal antrum? DRosenbach ^{(Talk | Contribs)} 05:02, 16 April 2010 (UTC)

Look at the pictures in either of the two articles you linked. There are two flaps at the top and bottom of the pharynx. The top is the uvula and the bottom is the epiglottis. During swallowing, both flaps are pushed away, blocking the relevent openings to either end of the breathing system. --Jayron32 05:21, 16 April 2010 (UTC)

Both pictures are midsagittal planes, rendering 2D images of 3D objects. DRosenbach ^{(Talk | Contribs)} 18:56, 16 April 2010 (UTC)

My original question does not seem to be answered: do other animals have a palatine uvula? If they do, then I assume that it has the same function of closing off the nasal passage during swallowing since no other animal seems to have the same sophisticated vocal language that we humans do. —Preceding unsigned comment added by 69.77.185.91 (talk) 16:57, 16 April 2010 (UTC)

Do plants need to sleep?

Is it healthy for plants to be out in the sunlight all day and then under a fluorescent light at night? Should they be left in the dark to sleep? Do they need to sleep? Specifically I was wondering about very young pumpkin plants. For the hell of it, I just started a couple plants in pots [soup tins].--Brianann MacAmhlaidh (talk) 06:49, 16 April 2010 (UTC)

From what I read after a google search it seems that the leaves will grow OK, but the constant light will mess with flower budding, and other plant stages. So you might get a big plant, but no pumpkins. You might be able to start with constant light and grow them fast, then switch to a normal pattern when it's time for flowers, but I'm not sure. In general plants use the ratio of dark to light to know what season it is, and they do different things at various points in the seasons. Ariel. (talk) 08:28, 16 April 2010 (UTC)

It depends on what type of photoperiodism your plant exhibits. Pumpkins are in the same family (taxonomy) as cucumbers, which according to our article are day-neutral i.e. they will flower in any light regime. I don't know whether this carries over to to pumpkins, or whether other physiological processes will be affected by constant light. 131.111.185.69 (talk) 09:26, 16 April 2010 (UTC)

Thanks for the replies Ariel and 131.111.185.69. I've searched about on Google for this, though it seems like no one really knows for sure. Pumpkins aren't really the type of plant people plant indoors, I guess. Hopefully they'll be in the ground by the time they start flowering.--Brianann MacAmhlaidh (talk) 06:13, 18 April 2010 (UTC)

Refractive index less than one

In Refractive index it says: "Contrary to a widespread misconception, n may be less than 1, for example for X-rays." But doesn't that imply a speed of light greater than c? The only thing I could think of is that for X-rays this is "n" as compared to air, not vacuum. Ariel. (talk) 08:20, 16 April 2010 (UTC)

The phase speed is greater than c, but that doesn't mean that a signal can be sent with such speeds. Remember that an idealized monochromatic wave actually extends to infinity (only then the Fourier transformation yields a single frequency). The propagation of a wave packet will be slower. Icek (talk) 11:02, 16 April 2010 (UTC)

To be more specific, the speed of light in a medium is actually given by

$v_{g}={\frac {c}{n-\lambda {\frac {dn}{d\lambda }}}}$

which will always be smaller than (or equal to) c even when n<1. Dauto (talk) 15:12, 16 April 2010 (UTC)

This is the only known example of "real" faster than c propagation of light. Count Iblis (talk) 20:58, 18 April 2010 (UTC)

The Leaning Brown Building of the Spanish Steps

Photo A

Photo B

In Photo A, the brown building on the left seems to be standing perpendicular to the ground, as you’d expect.

But in Photo B it’s very different. Obviously it’s a function of where the photographer was standing and the direction the camera was pointing. The vanishing point seems to be a foot above the picture, yet the camera was clearly not aimed at the vanishing point. How to explain the effect? -- Jack of Oz ... speak! ... 10:48, 16 April 2010 (UTC)

Perspective distortion (photography)? It looks in the second camera as if the person is tilting the camera up slightly (unless that's just my eyes) which can have the affect of making buildings lean/slope in funny directions. 194.221.133.226 (talk) 11:11, 16 April 2010 (UTC)

The metadata for the left photograph indicates it has been treated in Corel Paint Shop Pro where it could have received perspective correction to make the vertical edges of buildings parallel. Cuddlyable3 (talk) 12:09, 16 April 2010 (UTC)

Looks to me like the photographer was tilting the camera up in the second picture. The fountain in the foreground also looks wrong. Take a look also at a tilt shift lens. Ariel. (talk) 12:30, 16 April 2010 (UTC)

The second image was shot up the hill without perspective correction, either with a tilt-shift lens or via software. Since there's an angle upwards, the vertical lines will converge in accordance with the principals of perspective. Our brain tends to edit out such vertical perspective, but not horizontal perspective, which we expect as a natural phenomenon. Therefore, pictures that exhibit vertical perspective look odd. It's the bane of architectural photographers, since most buildings are taller than the photographer, so shooting up, if one is reasonably close, is inevitable. I routinely correct for vertical perspective in Photoshop, since I haven't brought myself to spend on a nice T-S lens. The Spanish Steps are on a steep hill, so the vantage point of the first image, off to the side, avoids the problem to some degree (anmd appears to have been further fixed in Corel), while the second is significantly lower than the base of the steps. Acroterion _(talk) 17:21, 16 April 2010 (UTC)

Thank you, Acroterion, that was a very clear explanation. -- Jack of Oz ... speak! ... 03:41, 18 April 2010 (UTC)

For answering questions like this, you may want to post a link from the Featured Pictures talk page. Those guys are experts at correcting and understanding all kinds of distortion effects. 64.235.97.146 (talk) 18:19, 16 April 2010 (UTC)

brain activity and dreams

Every action of ours is ordered by our brain. In dreams, if we do any action like eating, fighting etc., it is because of the brain's activity or our obeying the brain's order, of course mentally. In that case, why is the body in reality not obeying the order of the brain (i.e. why don't we eat or fight, waking up from sleep, as a result of the 'order' from our brain) ? And if it does, like in case of somnambulism or something like that, we call it a 'disorder'. Another question is that why don't most of us remember the dream that we dreamt that particular night, at once after waking up. (i would rather prefer to be a fool asking questions that are foolish) —Preceding unsigned comment added by 125.21.50.214 (talk) 11:16, 16 April 2010 (UTC)

I'm not an expert here, but I know there are different segments of the brain. One bit is controlled consciously, another is automatic. Dreams are a result of, I suppose, random thoughts being viewed. Most people do remember their dreams, but stress and other factors can cause us to forget. If we disobey the orders of the brain, we get tired, hungry, or injured. That's all I can help you with. Maybe there are some experts here. 2D Backfire Master ^{sweet emotion} 11:21, 16 April 2010 (UTC)

Sleep paralysis. During sleep the body "switches off" the nerves that would otherwise carry out the actions. If they don't switch off, then you have Sleep walking. And sometimes it will stay switched off for short time after waking, which is quite terrifying when it happens. (It's happened to me twice.) Ariel. (talk) 11:38, 16 April 2010 (UTC)

Wow, that sleep paralysis article is awful. I think it's talking about 2 different things and doesn't even know it. Comet Tuttle (talk) 20:43, 16 April 2010 (UTC)

Yeah, as the sleep paralysis article explains (although not very clearly), there is a special circuit in the brainstem that disconnects the upper brain from the lower motor centers during the dreaming state. In experiments using cats where this small brain area was damaged, the cats would physically enact their dreams. There is a caveat though: sleepwalking is actually a different phenomenon. The data is limited, but it looks like a sleepwalking person is not actually in the dreamlike state, but rather in a state where part of the brain is asleep while other parts are awake. Looie496 (talk) 17:45, 16 April 2010 (UTC)

Michel Jouvet is famous for his experiments in which he destroyed a portion of the lower brain stem in cats that caused paralysis during sleep; some cats then could be seen to act out their dreams. Until, presumably, they were woken up by all the tactile input of walking around. A quibble with your first statement: Not every action of yours is ordered by your brain. Healing, most (or all?) of the digestion process, and several kinds of reflexes are examples. Comet Tuttle (talk) 20:43, 16 April 2010 (UTC)

However, when people are only half-asleep sometimes they will be woken up by a mini "spasm" that coincides with the partially awake dream of the person falling, and some scientists link this to the ancestral fear of falling out of a tree while sleeping. Do we have an article on this? ~AH1^(TCU) 15:56, 17 April 2010 (UTC)

Yes, see hypnic jerk. Looie496 (talk) 17:00, 17 April 2010 (UTC)

Why can't plants move?

What in evolution made plants immovable? They prepare their own food but is it 'food' all they need? They depend on wind, insects, water etc., for pollination, they would have been lot more better (than the highly-evolved humans) had they been able to move since the time of evolution. - Anandh, Chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 12:07, 16 April 2010 (UTC)

How could they both move and have roots? I think once they have roots, they are committed to it. If you mean move branches, some plants do, but most of the time it's not very useful for a plant to be able to do that. Ariel. (talk) 12:14, 16 April 2010 (UTC)

Some plants are capable of rapid movement. See venus flytrap. As an aside, movement takes a LOT of energy, so there needs to be a really good reason to evolve such a capability. In the case of the venus flytrap, it lives in such poor soil it needs to catch bugs for nutrients. --Jayron32 12:41, 16 April 2010 (UTC)

See Rapid plant movement for a lengthier list. Gabbe (talk) 13:04, 16 April 2010 (UTC)

It is also important to think of plant movement speed based on plant lifespan. Consider a plant that can live for 1,000 years. If it moves a branch a couple feet in a year, that is relatively fast movement/lifespan compared to animals. Another way to think about it: Animals have a very short lifespan compared to plants. So, they have to quickly find food. Plants have time to wait for food. -- kainaw™ 12:46, 16 April 2010 (UTC)

Not really. Even if you assume a human is only going to move 50 years, he would only be able to move 20 yards a year, and that is incredibly slow. I bet even a snail could beat that in a week or two. Googlemeister (talk) 13:41, 16 April 2010 (UTC)

One might as well ask why humans can't generate their own food by just sitting in the sun, as that would clearly be a lot easier than running around and trying to brain other creatures with stones. --Mr.98 (talk) 12:48, 16 April 2010 (UTC)

See tumbleweed, sargassum and phytoplankton.--12:56, 16 April 2010 (UTC)

Photosynthesis doesn't really generate enough energy to move around like us animals do. If plants wanted to move and dance under their own power they'd need to find a new source of energy.

The Venus Fly Trap mentioned above can take hours or even days to "reset" its traps. APL (talk) 14:51, 16 April 2010 (UTC)

Who says that having movment means something is higher evolved? If you ask me, plants were here before humans and have evolved to make their own food, be self sefficient during a regular life cycle and reproduce by using the natural occurences of the Earth. If you ask me, they are much higher evolved. 74.218.50.226 (talk) 15:44, 16 April 2010 (UTC)

That debate came up while back when the DNA of rice was completely sequenced. Previously, there was an assumption that dna sequence length equated to level of evolution. However, rice sequence length is much longer than human sequence length. So, I saw some people assume that the rice sequencing was wrong and they wanted to resequence it to see if was actually much shorted. Others assumed human sequencing was wrong and wanted to resequence it to make it longer. Some assumed that equating evolution level to sequence length was hogwash and dropped that whole idea. A few wacky scientists said that it was all correct and that rice was more evolved than humans. As one put it: Try living all year standing knee-deep in a cold bog and see how long you survive. -- kainaw™ 15:49, 16 April 2010 (UTC)

The first plants to appear were algae. They floated in the sea, carried by currents, getting nutrients from the surrounding water and using sun energy from the sun. They were no animals yet, so they couldn't feed from them. There was no oxygen in the atmosphere yet, so they couldn't use it to make the energy transformation that us animals use now. Time passed, and algae filled the oceans and increased the oxygen content in the atmosphere. Some of the oxygen dissolved in the sea water. Now some pluricelled (is that the name in english?) livings discovered a mean to eat the algae and use the oxygen to process its components into lots of energy. Algae couldn't have discovered that process because the ingredients weren't there when they first appeared. All plants descend from those algae, and all animals descend from those algae-eaters. Our ancestors went down that path of evolution and we are pretty much stuck into it, for good or for bad. There are some very successful species that decided to test new grounds (like fish becoming amphibian when they first went to land, and later some big land animals deciding to return to the sea and becoming whales) but they still carry an awful lot of inherit traits, and they needed a lot of generations and ambient influences to change their shapes. --Enric Naval (talk) 16:50, 16 April 2010 (UTC)

Multicellular? Zain Ebrahim (talk) 17:00, 16 April 2010 (UTC)

In English, we call it a multi-celled plant or animal. StuRat (talk) 17:02, 16 April 2010 (UTC)

Mimosa (the plant, not the drink) is quite fast moving, but does not do so to eat flies like the Venus Flytrap. Edison (talk) 04:28, 17 April 2010 (UTC)

Just be grateful that they can't move. Mitch Ames (talk) 08:19, 17 April 2010 (UTC)

Because they grow places instead of going places. Why waste loads of energy moving (and making your muscles warm to do so) when you can just sit still? Also plants move their chloroplasts around their cells in response to varying light using the same proteins (actin and myosin) that are in our muscles. With regards as to which are more evolved, I like to think that plants make things (a huge variety of secondary metabolites) whereas animals break things. The idea of linear evolution is stupid, everything is adapted to the environment it lives in and the lifestyle is uses. 131.111.30.21 (talk) 10:45, 17 April 2010 (UTC)

Incidentally, remember that many animals are sessile too. --ColinFine (talk) 14:15, 17 April 2010 (UTC)

Some plants use forms of vegetative reproduction that enable them to "move" over time along their roots to create other members of the same organism, see quaking aspen. ~AH1^(TCU) 15:53, 17 April 2010 (UTC)

Just consider the word 'plant'. Something that's planted doesn't move without intervention. Vranak (talk) 22:17, 17 April 2010 (UTC)

Mind controlling gene function.

A person's character is based on genes (excluding environmental factors)(they say...like father/mother is the son/daughter)but character changes as years pass by. Does that mean the gene expression or gene function for the 'disappearing character' lost/stopped? If so, can one's mind control the gene expression so that it would be advantageous for one to evade baldness, fear etc., by controlling the baldness/fear gene's expression/function ? - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 12:26, 16 April 2010 (UTC)

Are you sure "A person's character is based on genes" is true? It's probably affected to some degree by it, but not controlled absolutely. This is a very very old argument, with no single answer, but you can read all about it in Nature vs. Nurture. Ariel. (talk) 12:32, 16 April 2010 (UTC)

Yes, son/daughter has father/mother's character. The reason obviously is through inheritance (genes of course). It hence means genes control characters, though not absolutely as mentioned by Mr. Ariel. - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 12:54, 16 April 2010 (UTC)

How can you be certain that sons & daughters don't have their mothers/father's character because they were raised by their mother/father and so learned that personality. What percentage of their character is because they have their parent's genes, and what percentage is because they were raised by their parents? --Jayron32 13:55, 16 April 2010 (UTC)

Agreed. Genes are a minor factor, with environment being the major factor, and there's also a small random element (we know this since identical twins raised together aren't quite identical in personality). Now, as for the genetic part, yes, they can express at different ages. For example, sexual orientation may not express until puberty or even later. However, this certainly doesn't mean that this gene expression can be controlled by conscious thought. StuRat (talk) 16:56, 16 April 2010 (UTC)

"son/daughter has father/mother's character". This proposition implies that all siblings have the same character. That's certainly not true in my experience, and in the US we have somewhat of a tradition of presidents with ne'er-do-well relatives. --Sean 17:06, 16 April 2010 (UTC)

When you talk about the mind controlling gene expression, you are improperly mixing levels in a way that can only lead to confusion. There are many factors that influence gene expression, including levels of stress-related hormones such as cortisol. Since stress is clearly a function of cognitive factors, there must be at least some degree of influence of cognitive factors on gene expression. It is important to point out, though, that a gene that is not expressed does not disappear -- it is still there, and will still be inherited. Also gene expression often differs greatly for different cells within a single body. Looie496 (talk) 17:36, 16 April 2010 (UTC)

Stephen Pinker has argued that behavioral studies tend to underplay the role that genetics has on behavior. Studies that show, for example, that reading to your children before bed boosts their scholastic aptitude don't control for genetics so it could simply be the case that families with genes that lend themselves to scholastic aptitude include the tendency to read to children at night.

Even if one's DNA has a stronger influence on behavior than we normally assume, it doesn't necessarily mean that it's particularly strong (especially when we have very strong environmental factors). In this TED talk, Jonathan Haidt talks about a postulated innate morality but, as he argues, innate doesn't mean fixed. It's just means that there's an existing template that our genes provide that experience then revises. This is also part of Derek Bickerton's language bioprogram theory regarding innate grammar. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 19:31, 16 April 2010 (UTC)

Genes have essentially no impact on your character. They might on your intelligence etc, but a son of two really popular and charismatic people might be a real loner who is afriad of social interaction simply due to the fact that he's never learned how to act appropriately in social situations (I know a guy like this with parents like that). Also twin studies are rubbish, the twins do not go through identicle upbringings. It would be exceptionally naive to assume they do. Siblings, twins, often have different interests and do loads of different things. One twin might be a great footballer and become a PE/Gym teacher. The other may be more academically orientated and go on to be some brilliant proffessor.--92.251.148.126 (talk) 22:50, 16 April 2010 (UTC)

Genes definitely have some sort of impact on temperament. The correlation is too strong not to notice. But they don't determine it. John Riemann Soong (talk) 02:54, 17 April 2010 (UTC)

There are loads of anecdotes of twins separated at birth who reunite to discover they have many many common characteristics. I recall one example where a pair reunited after living in different states for several decades to find that the only real [readily describable in a Readers Digest article] difference between their personalities was their favorite sports teams. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 19:14, 17 April 2010 (UTC)

Map of the world folded along the equator

Where could I find a map of the world where the southern and northern hemispheres are superimposed, so that the same latitude north and south of the equator is shown in the same place? This results friom a discussion on the Entertainment Desk about how far south Australia is compared to how far north Europe is. Thanks 78.151.110.54 (talk) 16:33, 16 April 2010 (UTC)

There's a couple in our antipodes article. See also www.antipodemap.com --Shantavira|^{feed me} 16:46, 16 April 2010 (UTC)

Let's split...

Which came first, the split between plants and animals or the split between single-celled and multi-celled ? Since we have all 4 combinations, that implies that one of those splits happened twice. Here is are some possibilities I see:

SP = Single celled Plants
MP = Multi-celled Plants 
SA = Single celled Animals 
MA = Multi-celled Animals

SP -> MP -> MA -> SA

MP                
^              
|
SP -> SA -> MA

StuRat (talk) 17:14, 16 April 2010 (UTC)

I think Multicelularity evolved more than once but I don't think SP -> SA makes any sense. Dauto (talk) 18:23, 16 April 2010 (UTC)

So then do you think that single-celled animals (de)evolved from multi-celled animals ? StuRat (talk) 19:24, 16 April 2010 (UTC)

More relevant, I think, is the monophyly of Eukariotic life. Having organelles within your cell structure isn't necessarily a prerequisite to multicellularity, but it certainly helps. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 19:22, 16 April 2010 (UTC)

According to newer research in the last decade, the presence of multicellular life is most likely directly dependent on organelles, with the mitochondria possibly allowing for the evolution of multicellular life. Sjschen (talk) 14:42, 19 April 2010 (UTC)

It is not as simple as that. The chloroplasts found in plants are believed to come from unicallular organisms that became part of plant cells during their evolution. And there are things that are neither animals nor plants. I take it that the OP did not study biology at school. 78.151.110.54 (talk) 19:26, 16 April 2010 (UTC)

"Which came first" is hard to answer, because it depends on how you define "plant", "animal", and "multi-cellular". Is a plant "something that obtains energy from non-living sources", or "something that obtains energy from the Sun"? Is an animal "something that obtains energy from its surroundings", or "something that obtains energy from other living things"? Is a multicellular being any grouping of attached cells, only those groupings where the cells interact, or is it further restricted to ones with some degree of specialization of the cells? What does a mat of chemosynthetic bacteria count as? --Carnildo (talk) 22:39, 16 April 2010 (UTC)

I'm not sure a mat of bacteria should count under the term multicellular...if that were the case the layer of slime in bathtub would be considered multicellular life. The term multicellular life to me should only apply to colonies of cells with tight collaboration and specialization of functions, including that of various somatic and sexual function. These cell colonies cannot be chopped up and still be considered an organism. For instance, if you divide up a bacterial mat, it becomes several segments of viable bacterial mat, but if you chop up a C. elegans it will not be a viable organism (it can grow back its parts but each divided part is no longer a whole organism). Slime molds are harder to pigeon hole, but since their cells collaborate so closely in reproduction, I would put them in as multicellular. Sjschen (talk) 14:42, 19 April 2010 (UTC)

Reading articles like prokaryote suggests that things can be both single- and multicelled, and that things did not simply split but there was a network of splittings and mergeings, and that no-one really knows which came first. 78.146.229.142 (talk) 12:16, 17 April 2010 (UTC)

Multicellular life most likely arose after the acquisition of mitochondria or chloroplasts with animals containing the former and plants containing both. If you use this definition than the first single cell eukaryotes are animals (SA) since acquisition of the mitochondrias is the first step to increasing energy output in relatively light free environments. The chloroplasts would be taken on later so: SA -> SP. While we can be sure that single cell plants produced multicell plants (SP -> MP) we don't know if it was single cell animals leading to multicell animals (SA -> MA) or a jack-of-all-things multicell plant through gamete mutation producing the proto-multicell animal(MP -> MA), though the former (SA -> MA) is more likely. Another possibility, though much less likely is SP -> SA -> MA, in which some SP lost its chloroplast after gaining some important adaptation which allows it to produce the modern SA that in turn evolved to MA.

Maybe it went something like:

SA-->SP-->MP
 | 
 --->MA

or

SA-->SP-->MP
           |
           -->MA

or

oldSAs-->SP-->MP
          |
          --->newSA-->MA

Likely only genetic and/or fossil studies can further elucidate this. Sjschen (talk) 15:07, 19 April 2010 (UTC)

Thanks. So it looks like it's still an open question. I thought plants must have come first, since animals need them to eat. Apparently, animals must have eaten other organisms, before there were plants. StuRat (talk) 17:19, 19 April 2010 (UTC)

The first living things were chemosynths, which don't really fit in either "plants" or "animals". --Carnildo (talk) 01:12, 20 April 2010 (UTC)

OK, but then how did we get from those to single and multi-celled plants and animals ? StuRat (talk) 13:42, 20 April 2010 (UTC)

football effecting brain

does taking heads(in football) harms your brain(means unabling the brain to do something,anything)?

but here is a simple explanation that when u take head there is jerk on ur head so damage is inevitable.

well i don't think so as our brain is well secured in a bony box ie skull and also for further safety there is 3 layered membrane filled with a fluid absorbing shocks.

I THINK IT IS JUST A MISCONCEPTION —Preceding unsigned comment added by Myownid420 (talk • contribs) 17:41, 16 April 2010 (UTC)

Well, you're wrong. The brain has a lot of protection, but it is so soft and squishy that a hard blow to the head can seriously damage it anyway. Looie496 (talk) 17:51, 16 April 2010 (UTC)

I remember reading some time ago that this is a danger and that professional footballers and others were advised to avoid them. Cannot recall where I saw it, but I often look at health section of the BBC news-site, and that would be the sort of thing they'd cover. 78.151.110.54 (talk) 18:38, 16 April 2010 (UTC)

Jeff Astle, one of West Bromwich Albion's most famous players, died from a brain disorder which was ascribed at the inquest to repeatedly heading a football. I would point out, however, that he was active in the 1960s and 70s when footballs were made of leather and became even heavier in wet English conditions. [6] --TammyMoet (talk) 19:19, 16 April 2010 (UTC)

See Dementia pugilistica. At the bottom of the article it notes that it's been diagnosed also in player(s) of American football and professional wrestling. Comet Tuttle (talk) 20:47, 16 April 2010 (UTC)

Yes it certainly does, and those are just the first four google hits. ~ Amory (u • t • c) 20:52, 16 April 2010 (UTC)

45% of some professional footballers tested had brain injuries from heading, according to http://news.bbc.co.uk/1/hi/health/176392.stm 78.146.229.142 (talk) 12:19, 17 April 2010 (UTC)

See also concussion. ~AH1^(TCU) 15:50, 17 April 2010 (UTC)

Closed head injuries regularly result in brain damage. Yes, the structure of the brain cavity is such as to provide a good deal of protection, but that doesn't mean it's set up to take repeated and/or intense impact. The hardness of the skull may even serve to damage the brain as much as to protect it (as in contrecoup injuries, which often result in worse damage from the brain bouncing around inside the skull than from the impact itself). A friend of mine who used to volunteer at a rehabilitative clinic told me that some of the brain-injured individuals there suffered severe and permanent damage from activities as innocent as getting out of bed, slipping on the rug, and striking the head on the edge of the nightstand. It seems logical, then, that there would be at least an element of risk in an activity that involves a sizable, fast-moving object colliding with the head. See Association football headgear. Furthermore, although most people who have suffered a concussion or two in the course of their lifetime recover with no lasting effects, frequent concussions may lead to neurodegeneration (the abovementionted dementia pugilistica). When the brain suffers a concussive blow while still under the effects of a previous concussion, death or permanent damage is possible from a rare condition called second-impact syndrome, most often seen in young athletes. If you do play a sport that puts you at high risk for concussion (football/soccer, American football, boxing, etc.), be familiar (and make sure your teammates are familiar) with the symptoms of concussion and DON'T RETURN TO THE GAME after a head injury until you've been medically cleared. 71.104.119.240 (talk) 21:06, 20 April 2010 (UTC)

Movie about the "representative town in sampling"

I have a vague recollection there is a movie about a town (in US) that was seen for a time as a very representative town, with regards to sampling (it's population was seen as very "average"). Half an hour of googling and looking through Wikipedia categories and articles gives me nothing. Any suggestions? --_{Piotr Konieczny aka Prokonsul Piotrus| talk} 17:54, 16 April 2010 (UTC)

Will_it_play_in_Peoria?#Peoria_as_test_market -- Coneslayer (talk) 17:58, 16 April 2010 (UTC)

Interesting, but I see nothing about a movie. I am pretty sure I read about something similar in the context of a movie made of it (or a book? Hmmm.). --_{Piotr Konieczny aka Prokonsul Piotrus| talk} 18:47, 16 April 2010 (UTC)

I googled for "most typical american city" (as four words, not a phrase) and that quickly turned up the key word "Middletown". In Wikipedia, Middletown links to Middletown studies, which links to Magic Town, which I believe is the movie you want. --Anonymous, 05:22 UTC, April 17, 2010.

Yes, I believe this is what I was looking for. Thank you both, --_{Piotr Konieczny aka Prokonsul Piotrus| talk} 06:08, 17 April 2010 (UTC)

Largest Recorded Solar Flare

When was the largest recorded solar flare? According to this, it was recent. But according to this, it was in 1972. --Reticuli88 (talk) 18:46, 16 April 2010 (UTC)

The recent one seems to have been measured with a new device. Also, the wikipedia article could be outdated. Most other sources cite the 2003 one. --Cheminterest (talk) 00:46, 17 April 2010 (UTC)

The Carrington Event in 1859 was likely the biggest geomagnetic storm ever recorded from a solar flare that hit the Earth. ~AH1^(TCU) 15:48, 17 April 2010 (UTC)

Escape velocity

Escape veocity is said to be the amount of speed necessary to escape an body's gravitationa (or whatever) field. This is usually said to be independent of the launch angle, because kinetic energy is a function of the speed, not velocity, of an object. I think this is a mistake though. If an object were to be launched at an angle to the horizontal, even though it may have the energy necessary to reach an infinity height, its trajectory won't allow it to, because when it reaches its maximum height, it will still have some speed, just perpendicular to the direction of gravity. Am I right? Does the radial component of the velocity have to equal the escape velocity? 173.179.59.66 (talk) 20:11, 16 April 2010 (UTC)

You are right. Wikipedia has an article about Escape velocity. Cuddlyable3 (talk) 23:19, 16 April 2010 (UTC)

But the article indicates that the object will undergo a parabolic trajectory if shot at an angle, which would take it to infinity, no? 173.179.59.66 (talk) 00:18, 17 April 2010 (UTC)

The article is right. The component of the velocity perpendicular to the direction of gravity will steadily decrease as the object moves away from the planet allowing the object to scape. Just remember that the direction of gravity is changing as the object moves along the orbit. Dauto (talk) 01:25, 17 April 2010 (UTC)

In the case of a spherically symmetric 1/r² field, the closed (elliptical) orbits all have a total energy smaller than the escape energy, so whether you get a closed or open orbit does depend only on the speed. In general, though, there can be closed and open orbits passing through the same point with the same speed, in which case it does matter which way you throw. (But can that happen in Newtonian gravity in 3 dimensions? I don't know.) -- BenRG (talk) 05:19, 17 April 2010 (UTC)

To put it plainly, the original poster is wrong and Cuddly is wrong to agree. As long as the object is not slowed by collision or by air friction, its direction doesn't affect whether it will escape or not, only its speed does. The original poster's reference to "its trajectory won't allow it" appears to assume that it will start falling, but it never will. --Anonymous, 05:30 UTC, April 17, 2010.

What I meant by "its trajectory won't allow it" is the following: suppose we are dealing with an object travelling near the earth's surface. If we want this object to reach a height h, buy the conservation of energy we want the ball to have a speed v = sqrt(2gh). But this will only work if the object is shot up perpendicular to the surface. If it is shot at a bit of an angle, then its apex will lower than this max height.

Now when it was originally presented to me, the escape velocity was calculated by the conservation of energy. That is, mv²/2 = GMm/r, and solve for v. However, it is then said that, because speed is a scalar and doesn't depend on direction, this works regardless of the angle it is launched at. However, drawing a parallel to the example I gave above, it seems perfectly reasonable that an object launched at the escape velocity at an angle won't reached r = infinity (ie its maximum height), even though it would have the energy to do so. So it appears, at least to me, that further analysis is required to justify that escape velocity is independent of launch angle, beyond looking at potential and kinetic energy. Is this correct? 173.179.59.66 (talk) 06:04, 17 April 2010 (UTC)

The only reason the object might not "escape" at lower angle is that it would remain in the atmosphere for longer, and would thus lose some of its initial energy, bringing its "total energy" below escape energy. On a (spherically symmetric) planet (see comments below) without atmosphere or mountains, escape velocity will allow escape at any angle above zero. Dbfirs 08:41, 17 April 2010 (UTC)

The OP is right, as I said above. In, say, a spherical 1/r⁴ field, circular orbits have a total energy that's larger than the energy at infinity, but they're nevertheless closed (though unstable—but you can construct a potential where they're stable too). That doesn't happen in Newtonian gravity in three dimensions with spherical symmetry, but it's not self-evident that that's the case. I don't know if it can happen in Newtonian gravity in three dimensions without the assumption of spherical symmetry. -- BenRG (talk) 10:18, 17 April 2010 (UTC)

Energy calculations do not take into account the physical size or shape of the Earth (or other planet). If you launch an object exactly horizontally with a speed greater than escape velocity then it enters a hyperbolic orbit whose perigee is at the launch point (because launch is horizontal). This is its closest approach to the center of the Earth. So as long as you assume a spherical Earth (and, of course, no atmosphere) then yes, the object will escape to infinity, even though initially it has no radial velocity - this is illustrated at the top of the escape velocity article. But if you have a non-spherical Earth (and the OP seems to be assuming a flat Earth) or launch at an angle below the horizontal then the orbit may intersect the surface of the Earth at some point after launch - conservation of energy does not forbid this. This is what escape velocity#Orbit says - an object can be above escape velocity but not on an escape trajectory. Gandalf61 (talk) 11:12, 17 April 2010 (UTC)

Okay, I see what you're getting at now with the "trajectory" thing. When we're talking about objects near the Earth's surface moving at moderate speeds, it is indeed true that if you launch an object diagonally instead of vertically, it won't rise as high. That's because only the upward component of its initial velocity is directed opposite to the gravitational acceleration, so it's eliminated sooner while the horizontal component remains unchanged. You can easily compute that, ignoring air friction, its path is a parabola.

But that analysis is based on the assumption that the Earth is flat! This is good enough for that particular case, but it's not the truth. That "parabolic" curve is actually the tip of a long narrow elliptical orbit reaching down inside the Earth, with its other end just beyond the Earth's center.

When you're dealing with an object moving at escape velocity, you can't ignore the shape of the Earth any more. If you imagine a trajectory where the object does not go on rising, that trajectory must be an orbit -- an ellipse. And for any particular orbit, there is only one possible speed for an object at any particular point in that orbit. And if you calculate the speed your object has remaining after it has risen to any particular altitude, it will always be faster than the speed for that point on any elliptical orbit.

To really prove it it'd be necessary to do the calculations, which I'm not going to attempt now, but I hope this explanation will at least help make it more intuitive why it works as it does.

Oh, one more point I should have made. Ignoring air friction, once an object is launched at a particular speed, its speed from then on is only a function of its altitude. For example, say you launch a ball vertically at 70 mph and at a certain height it has slowed to 30 mph. If you launch it diagonally at 70 mph and it reaches the same height before it starts dropping, then its speed at that height will again be 30 mph. The tradeoff between kinetic and potential energy is the same no matter what path it takes, right? Well, when I said that the speed would be too fast for it to be in an elliptical orbit, this principle explains how you would know what the speed will be. --Anonymous, 11:51 UTC, April 17, 2010.

So if I understood what was said, it would take a study of orbital mechanics and Newtonian gravity to understand the escape velocity result, right. Thanks a lot! 173.179.59.66 (talk) 15:27, 17 April 2010 (UTC)

Well no, just understand that the Earth is round. Even if you are moving mostly horizontally you will eventually be moving away from the Earth. John Riemann Soong (talk) 19:06, 17 April 2010 (UTC)

Also instead of thinking of maybe a rocket and Earth, think an electron and an atomic nucleus. (The nucleus is massive enough that it moves very slowly in our timeframe.) For a certain velocity less than V_e, you can even orient it totally vertically and it would be in a degenerate orbit (passing right through the nucleus) and you will get an orbit oscillating along the y-component. This excludes any quantum mechanical effects, of course. John Riemann Soong (talk) 19:13, 17 April 2010 (UTC)

It's just amatter of conservation of energy and angular momentum. Dauto (talk) 03:27, 18 April 2010 (UTC)

beer

i quit drinkin. whats the best tasting brand of non-alcohol beer sold in the usa? —Preceding unsigned comment added by Jonny12350 (talk • contribs) 21:42, 16 April 2010 (UTC)

i found a list of them please choose which i should buy

http://www.wegmans.com/webapp/wcs/stores/servlet/ProductListView?forwardto=ProductListView&Ne=5&Ntt=non-alcoholic%20&langId=-1&Ntk=ProductSearch&storeId=10052&Ntx=mode%20MatchAllPartial&catalogId=10002&N=207&Nty=1 —Preceding unsigned comment added by Jonny12350 (talk • contribs) 21:46, 16 April 2010 (UTC)

This is impossible to answer. The best one for you is the one you like the best (other factors such as cost, availability and so on being taken into account). Put your question another way: "what is the best tomato I can buy"? and you'll see there's no sensible answer. However in my experience (yes, this is original research) all non-alcohol beers are easily describable as "worst". Drink soda or fruit juice instead. Tonywalton ^Talk 00:21, 17 April 2010 (UTC)

The best non-alcoholic beer ? Root beer. StuRat (talk) 01:59, 17 April 2010 (UTC)

Corona (beer). Pretty much non-alcoholic. 173.179.59.66 (talk) 06:10, 17 April 2010 (UTC)

No, it isn't. Dauto (talk) 19:59, 17 April 2010 (UTC)

Speaking of root beer, don't forget about ginger ale. ~AH1^(TCU) 15:45, 17 April 2010 (UTC)

Looks like this is your chance to try a few different brands of non-alcoholic beer - and other beverages - until your taste buds make their expert decision. Have fun. 71.104.119.240 (talk) 21:12, 20 April 2010 (UTC)

Help comprehending units of energy

I can visualize most physical units, for example, I know about how much force a Newton is ("It's like me pressing down this hard"). However I find it very hard to comprehend a joule. Obvioulsy something that is moving has kinetic energy, but how do we quantify it? I am having trouble understanding exactly how much energy a "joule" is, probably because energy doesn't seem like something that one can have "amounts" of. I know this is an extremely hard request but can any of you help me visualize energy?--92.251.148.126 (talk) 23:00, 16 April 2010 (UTC)

Run up a mountain all day without eating. Do you feel hungry? Now you know what energy is. Cuddlyable3 (talk) 23:16, 16 April 2010 (UTC)

Yeah I knew what it was but "how much" is a joule? It doesn't seem to be something quantifiable.--92.251.148.126 (talk) 23:17, 16 April 2010 (UTC)

Why doesn't Orders of magnitude (energy) help? For that matter how about the Calorie? Nil Einne (talk) 00:05, 17 April 2010 (UTC)

I kind of take 92's point. Is it because a unit like a Calorie is defined in terms of other quantities? For example in the definition of the Calorie: the amount of energy required to raise the temperature of one kilogram of water by one degree Celsius one can directly perceive what a kilogram feels like (lift a bag of sugar) and what a temperature rise feels like (OK, perhaps not a 1°C rise, but you can directly perceive a temperature change), but you can't directly feel, see or hear the energy making the change. Tonywalton ^Talk 00:31, 17 April 2010 (UTC)

A joule is defined as the work done when a force of one newton pushes an object one meter, or one coulomb of electrons (a very large number) is pushed through a voltage of one volt. --Cheminterest (talk) 00:50, 17 April 2010 (UTC)

There we are again. The quantities you mention as defining a joule are physically palpable; you can feel a force (whether or not you can accurately tell whether it's 1N) and you can see, or walk, a distance. 92, might the article on Dimensional analysis be of interest? By the way, I'm not sure about your definition of a joule there, Cheminterest; surely the mass of the object you're pushing comes into it somewhere, and isn't work measured per time? Tonywalton ^Talk 01:03, 17 April 2010 (UTC)

Cheminterest's explanation is correct, the mass of the object is irrelevant for the definition of work. It is power that is the quatity defined as energy per time. You asked about how to better understand the unit of energy but what you really want is to understand the concept of energy. Once you do that, then the units will make more sense. Sure, energy is slighly more abstract than force or distance, but only slightly so. Dauto (talk) 02:27, 17 April 2010 (UTC)

Apologies, of course it's correct. My fault entirely for misreading it. Tonywalton ^Talk 00:12, 21 April 2010 (UTC)

If an average sized apple has a weight (not mass) of 1N on Earth then you lifting that apple up by 1 metre would mean you have done 1 joule of work to that apple. --antilived^{T | C | G} 13:43, 17 April 2010 (UTC)

We have Joule#Practical examples. It is fairly self-explanatory. (Except maybe the one with a drop of beer, which is a bit counter-intuitive, no pun intended. Beer has about half a kilocalorie of food energy per gram; that is roughly 2 kilojoules of food energy per gram. A beer drop that weights about 0.05 gram has about 100 joules of food energy. Not all of it can be used for work, of course, so a drop of beer is probably not enough for you to throw a 2 kg projectile at 10 m/s). --Dr Dima (talk) 06:20, 17 April 2010 (UTC)

c and si

C(carbon) and Si lie in same group.why compound co(carbon mono oxide ) is formed but SiO is not formed .plz explain —Preceding unsigned comment added by 119.154.126.225 (talk) 23:35, 16 April 2010 (UTC)

Actually, it does. See Silicon monoxide. It's just quite rare as it is not very stable (neither is CO, which is why it is not formed in nature. But cars don't burn silicon). Hope this helps, --The High Fin Sperm Whale 00:22, 17 April 2010 (UTC)

That's "quite rare" under normal Earth conditions (we have an atmosphere fairly rich in oxygen, after all, which tends to oxidise most things given half a chance). The article you linked states that "... [SiO] has been described as the most common oxide of silicon in the universe". Wish cars did burn silicon. Stuffing rocks into the tank would be much cheaper than using petrol, and rocks are easier to find than crude oil. Tonywalton ^Talk 00:40, 17 April 2010 (UTC)

About your note about rocks burning silicon: Rocks already contain silicon in an oxidized state. It cannot be burned any more, just like carbon dioxide cannot be burned. An oxidizible silicon compound such as SiO or silane would be a fuel, though. --Cheminterest (talk) 00:52, 17 April 2010 (UTC)

Good point, though CO₂ can be burned; just stuff something hot enough and oxygen-greedy enough into it (a lump of burning magnesium will do the trick, you get magnesium oxide and soot, aka carbon). I wonder if anything cheap could provide enough energy to dissociate SiO₂ in the same way, thus providing silicon out of my car's exhaust pipe which I could sell to Intel or TI. Hmmm...Tonywalton ^Talk 01:17, 17 April 2010 (UTC)

Anything strong enough to reduce silicon oxides (or carbon dioxide) isn't going to be found in nature: it would have long ago reacted with oxygen. If you did find something that strong, you'd just burn it instead (in oxygen) to get much more energy released. Buddy431 (talk) 14:13, 17 April 2010 (UTC)

You aren't burning the CO2, you are burning the magnesium. The CO2 would be the oxidizer (not the fuel). Ariel. (talk) 01:59, 18 April 2010 (UTC)

Jets in front of wings

All modern jetliners have jet engines that are placed well in front of the front edge of their wings. Why? —Preceding unsigned comment added by 71.70.143.134 (talk) 02:14, 17 April 2010 (UTC)

This is mostly speculation on my part, but I suspect weight distribution is at least part of the reason. Modern jetliners all use Tricycle gear arrangements, with the rear landing gear situated in the area of the wing. The center of gravity must be in front of the rear landing gear or bad things might happen, so pushing the fairly heavy engines, also mounted to the wings, as far forward as possible is presumably helpful. Also due to the shape of an airplane wing there is more strength near the leading edge, so pushing the engine nacelle forward makes sense. The engine nacelle itself should be attached at it's own center of gravity to keep it from torquing the wing, so if it is fairly long and attached near the front of the wing (where the wing is strongest) it's no surprise it might stick out. It probably also makes it easier to do maintenance on the engines. Winston365 (talk) 06:44, 17 April 2010 (UTC)

False premise. McDonnell Douglas MD-80 is a modern aircraft with rear mounted engines. Dragons flight (talk) 07:28, 17 April 2010 (UTC)

Sure, there are a bunch of airliners with rear mounted engines, although these days they are mostly for smaller aircraft (very common on business jets for example). These planes compensate by moving the wings farther towards the rear. Larg airliners these days put the nacelles on the wings though, which was implicit in the question asked. If you use engines mounted on the tail you can move the rear landing gear back as far as you need to to balance the aircraft, which also moves the wings towards the rear, but if you do decide to mount the engines on the wings that doesn't help as much, as moving the landing gear towards the rear of the aircraft would also move the engines back. Winston365 (talk) 07:45, 17 April 2010 (UTC)

Aircraft, and particularly high speed aircraft, are vulnerable to a potentially-destructive phenomenon called flutter. Aircraft designers aim to ensure the minimum speed for onset of flutter is well above the maximum speed of the aircraft. There are various modes of flutter and many of them can be avoided by ensuring the center of mass of the relevant part of the structure is ahead of the elastic axis of the part of the structure. For example, hinged control surfaces (ailerons, elevators and rudder) usually have lumps of lead (or depleted uranium!) attached to their forward edges to move the center of mass of the surface forward of where it would otherwise be. The more mass that is added means the higher is the flutter-onset speed.

Flutter of the wing can be avoided by ensuring the mass of the wing is well forward of the torsional axis of the wing. For this reason, aircraft designers place the engines well forward of the wing, on pylons. The further forward that the engines are located the higher will be the flutter-onset speed. This is just as true of turbo-props as jets. Note the location of the engines on the Vickers Viscount and P3 Orion. The further out along the wingspan that the engine is located, the more important it is to be located well ahead of the wing torsional axis. Some British aircraft had their engines buried in the wing root and the engines could be located near the trailing edge of the wing eg de Havilland Comet and the V bombers.

Similarly, high speed aircraft with fuel tanks on the wing tips must have the tanks protruding significantly forward of the leading edge of the wing. See the image at Learjet 25.

Another option is to have very stiff wings of relatively short span. That way, it is not critical that the engines be located forward of the wing. Concorde is an example of this third option. Dolphin (t) 08:30, 17 April 2010 (UTC)

The critical thing in any aircraft design is that the center of gravity be close to the center of pressure of the wing. (Generally, the 'center of pressure' is at the thickest part of the wing - a little way back from the front edge). If you imagine the lift from the wing pulling the plane upwards at the center of pressure - and gravity pulling it down at the center of gravity - you an easily imagine why you'd want those two points to be at the same place if you want the plane to be stable and to fly straight. So the entire issue of "balance" that everyone has been talking about relates to keeping those two points close together. Concord has triangular wings - the center of pressure is much further back than on a typical subsonic airliner - hence the engines need to be further back to keep a reasonable balance. SteveBaker (talk) 15:05, 17 April 2010 (UTC)

SteveBaker's comment is a popular one, but not entirely correct. On an airfoil of symmetric cross-section the center of pressure stays in a fixed location, usually around 25% of the chord, but on a cambered airfoil the center of pressure moves as the angle of attack changes. At high angles of attack (such as at low airspeed) the center of pressure is at its most forward position. But as the angle of attack reduces (such as when the airspeed increases) the center of pressure moves backwards, and may even lie behind the trailing edge of the wing! See Movement of center of pressure. It is impossible (and unnecessary) to always have the center of gravity close to the center of pressure because the center of pressure moves through significant distances during a flight.

To simplify the analysis of airfoils and aircraft stability, it is fortunate that there is a point that doesn't move and that helps determine the best position for the center of gravity. This point is called the aerodynamic center. For positive stability, the center of gravity should always lie within the specified range relative to the aerodynamic center.

However, back to the original question. The location of engines and wing-tip fuel tanks on the wings of aircraft is related to the avoidance of flutter, not ensuring the center of gravity of the aircraft is within the specified range. Dolphin (t) 02:49, 18 April 2010 (UTC)

April 17

Space elevator

Why does the center of mass of the space elevator have to at the Earth's geosynchronous orbit? I realize that it's to minimize tension forces acting on the elevator, but my confusion is the following: I understand that a particle in that orbit will be rotating at the same rate as the earth, but for an extended body such as the space elevator, I didn't think that was true. I thought treating the gravitational force as acting at the center of mass was only true for spherical or elliptical bodies. If I don't make sense let me know. 173.179.59.66 (talk) 07:25, 17 April 2010 (UTC)

The motion of any rigid body can be considered as a combination of the linear or orbital motion of the centre of mass (considering all forces as acting through the centre of mass), and the rotational motion about the centre of mass (considering the moments of forces about the centre of mass). It doesn't just apply to symmetrical bodies. At this scale. there might be a very small relativistic correction, and an adjustment because the centre of mass does not coincide with the centre of gravity, but the basic principle still applies and gives a reasonably accurate approximation. Dbfirs 08:26, 17 April 2010 (UTC)

Not correct. The force, and thus acceleration, on a non-spherical body is not the same as the force on a point mass at the body's center of mass. --99.237.234.104 (talk) 01:38, 19 April 2010 (UTC)

Centre of mass and centre of gravity mean exactly the same thing, don't they? --Tango (talk) 11:59, 17 April 2010 (UTC)

Normally, yes. But I think here the different (lower) gravity at the top of such a object means that the average centre of gravity is lower than the centre of mass. Our article, centre of mass, says "The center of mass is often called the center of gravity, but this is only true in a system where the gravitational forces are uniform.", I assume this is what it means. - Jarry1250 ^{[Humorous? Discuss.]} 12:19, 17 April 2010 (UTC)

Ah, yes. I suppose that makes sense. I'm not sure the concept of a centre of gravity is useful in that context, though. --Tango (talk) 14:01, 17 April 2010 (UTC)

Also note that there's another good reason to have a "station" at the geosynchronous height: so that space ships can dock there. At any other height any ships in orbit would zip past the station. Depending on the relative size of this station, it might be a substantial portion of the overall mass of the elevator. Also, at the geosynch height, it shouldn't exert any net force on the elevator shaft, which is a big plus. StuRat (talk) 13:40, 17 April 2010 (UTC)

The station (or something) needs to be above geosynchronous height in order to compensate for the cable below it. A large station would only have to be a tiny bit above, though. Once alternative suggestion is to have the cable continue a long way past geosynchronous height. A craft on a cable above that height would be accelerated upwards by centrifugal force (and yes, it does exist in the most natural frame of reference for this problem, which is one that co-rotates with the Earth). That gives you a very energy efficient way of reaching an Earth escape trajectory. --Tango (talk) 14:01, 17 April 2010 (UTC)

I understand the practical benefits of having the space elevator at a geosynchronous orbit, but my issues are more physics related. If external forces are applied on an object, then the object's center of mass will accelerate just as if all the mass were concentrated at that one point. Now, a small object (like a space shuttle) at a geosynchronous orbit will have the right combination of acceleration and orbital distance so that it's orbital period matches the rotational period of Earth. But if the space elevator's center of mass is at the same location, because its acceleration will be much bigger, then it seems to me that it won't be in a geosynchronous orbit. I would think that the center of mass ought to be higher than the geosynch orbit, but this doesn't seem to be the case, and I don't know why. 173.179.59.66 (talk) 18:12, 17 April 2010 (UTC)

Why would the acceleration be much bigger? The acceleration will be "g" (adjusted for height) whatever the mass, and whatever the size except for the correction for non-uniform gravity. Can anyone find a reference for the integration of gravitational attraction over a typical mass distribution of a space elevator? (I should be able to do this myself, but I'd probably get it wrong.) I would estimate that the centre of gravity will still be not far from the centre of mass, but the difference might be significant. Dbfirs 20:36, 17 April 2010 (UTC)

If you have a really heavy station at the top then the mass of the cable probably isn't very significant. --Tango (talk) 21:12, 17 April 2010 (UTC)

Yes, I agree that it will probably not be worth worrying about in that case. Dbfirs 21:33, 17 April 2010 (UTC)

... though I think that the torque produced by gravity (on a centre of gravity just below the centre of mass) should have the effect of keeping the elevator vertical, rather like a ship with the centre of gravity below the metacentre. (Do we have any experts on the dynamics of rolling ships who could check my theory?) Dbfirs 20:47, 18 April 2010 (UTC)

Yes, that would be true in uniform or variable gravity - just consider a pendulum. I think the force on the cable due to it being attached to the Earth would also keep it vertical and would probably be a bigger factor. --Tango (talk) 21:51, 18 April 2010 (UTC)

No! A pendulum is suspended from a fixed pivot well above its centre of mass. A "pendulum" suspended at its centre of mass will rotate at random or remain at rest in any orientation. Similarly, an object in any orbit is likely to turn at random unless it has some mechanism for keeping a fixed orientation. Does a space elevator have the cable attached to the Earth? Dbfirs 22:48, 18 April 2010 (UTC)

Ok, a pendulum is a bad example. It is still true, though. It is a result of tidal forces and is responsible for tidally locked moons often having their denser halves pointing towards the parent planet (an object with non-uniform density is roughly equivalent to a non-spherical one). Yes, the cable is attached to the Earth. I think the force is usually fairly small at that point, but it has been suggested that you could move the cable around to avoid space debris by having it attached to a moving platform, so the force can clearly by non-zero. --Tango (talk) 23:50, 18 April 2010 (UTC)

Yes, I think we are in agreement that gravitationally locked moons with a constant face to the centre of orbit are observable, but I suspect that the reason for the locking is non-uniform gravity, not non-uniform density, because they would tend to rotate about their centre of mass, not their centre of volume. (Tidal forces will have caused the slowing of rotation in the first place.) If the cable is attached to the Earth, then there is no problem anyway, except in designing incredibly strong tethers! The engineering problems seem vast (though not necessarily insurmountable). Dbfirs 08:26, 19 April 2010 (UTC)

health/meth/sex/ed

(Removed question asking for medical advice) SteveBaker (talk) 14:55, 17 April 2010 (UTC)

Dude, I sympathize with your problems. Unfortunately we're not allowed to give medical advice like this on Wikipedia. I recommend you make an appointment to see your doctor. Axl ¤ [Talk] 11:14, 17 April 2010 (UTC)

(Removed medical advice) SteveBaker (talk) 14:53, 17 April 2010 (UTC)

Communicating dates to future civilizations

I'm sure someone must have thought about this before. Say we want to create a carefully protected archive of information related to our civilization so that even if most of the artifacts of our civilization are destroyed, future civilizations can still learn about our civilization and its history. Future discoverers of the archive will have to learn the language in which the archived materials are written. Numbers and formulas for chemical elements are quite easy to explain. But what about dates in historical records? How can we communicate to future civilizations which trip around the sun is year 2010 in our calendar? I guess we can keep some samples of carbon together with precisely measured radioactivity values and the measurement date, but that's probably not accurate enough to allow someone in the future to determine that year 2010 was 610432 earth-years ago. What better methods are available? —Preceding unsigned comment added by 98.114.98.221 (talk) 17:01, 17 April 2010 (UTC)

You could record the exact position of each planet. I don't know how often all 8 planets (aw, what the heck, toss in Pluto, too) repeat the exact same position, but it can't be very often. StuRat (talk) 17:17, 17 April 2010 (UTC)

The locations of stars would also help. The proper motion of stars is very slow, so by comparing our star charts with their own, they could tell roughly how much time had passed. They could then use the planets or something to narrow it down. --Tango (talk) 18:24, 17 April 2010 (UTC)

We could place stones in certain positions so that, when looking towards a certain direction over one of the stones, certain star constelations appear over the other stones. Then engrave in the stones which constelations appear in which dates. --Enric Naval (talk) 19:27, 17 April 2010 (UTC)

Does the Moon's orbit decay? If so, just record exactly how far from the Earth it is. Or, give our best estimate of the state of the Sun. There's a predictable progression of stellar composition from Hydrogen to the heavier elements as it runs out of fuel. Vranak (talk) 22:14, 17 April 2010 (UTC)

The Moon's orbit does decay (outward), but the change per year is tiny compared with the values you get with different methods of measuring it. StuRat (talk) 22:20, 17 April 2010 (UTC)

I think the moon's orbit decays inwards, so it is getting nearer earth, and it can be accurately measured by using the lazer reflectors left there by various moon missions. 78.147.241.153 (talk) 22:44, 17 April 2010 (UTC)

No, it decays outward. It can be measured accurately now, using the laser system, but a thousand years from now the Moon reflector will be buried in dust and the Earth station will be gone. An advanced civilization could set up a similar system, but the heights at both ends would be different from the current heights. StuRat (talk) 22:48, 17 April 2010 (UTC)

The Pioneer spacecraft carry information about the date and position from which they were sent as follows. There is a schematic drawing of the hydrogen atom and the 21 cm transition which defines a symbol for the unit of frequency that correpsonds to that 21 cm transiton. Then there is a drawing of pulsars with their frequencies showing where they are relative to Earth. If the Pioneer spacecraft are intercepted by some advanced civilization a million years later, they can not only tell from where it came from but also when it was launched using the spin down rates of the pulsars. Count Iblis (talk) 23:01, 17 April 2010 (UTC)

A fairly exact chronology of the Twelfth dynasty of Egypt was established based on clues left behind based on their references to astronomical events such as the heliacal rising of Sirius and to phases of the moon. See The Calendars of Ancient Egypt by Richard Anthony Parker. Gabbe (talk) 09:38, 18 April 2010 (UTC)

Head Hair

?Are there any disadvantages to not washing ones head hair for a long time (say 6 months)?--79.76.233.217 (talk) 17:17, 17 April 2010 (UTC)

Lice, ticks and fleas to name a few. --The High Fin Sperm Whale 17:24, 17 April 2010 (UTC)

You'll have to cite a source if you are claiming that these are prevented by head washing. I think they are prevented by avoiding such critters. Lice, in particular, aren't eliminated by normal head washing, otherwise there'd be no need for lice shampoo and those superfine lice combs, and the alerts in the elementary schools when, horrors, one of the kids is found to have head lice. Comet Tuttle (talk) 19:10, 17 April 2010 (UTC)

It tends to get greasy, smelly, and itchy. StuRat (talk) 17:29, 17 April 2010 (UTC)

Here's someone who conducted a similar experiment, though she also avoided showering and using deodorant. Google is failing me on my search for the person who I believe was a UK Member of Parliament who "outed" himself as not having washed his hair for the last decade, and claimed he had suffered no adverse effects, social or otherwise — anyone know who I'm referring to? Comet Tuttle (talk) 19:09, 17 April 2010 (UTC)

Didn't fail me... Matthew Parris - [7]. He does say he rinses it with water every day, but doesn't use shampoo. Ghmyrtle (talk) 19:18, 17 April 2010 (UTC)

I think the main disadvantage is a reduced social life. Some might be able to get away without it, depending on their kind of hair. I'm not one of them. Dauto (talk) 20:11, 17 April 2010 (UTC)

Exactly, it depends on the person. I've heard quite a few accounts of this sort of behaviour and it seems to work out for the best, although some people eventually do go back to washing. For middle-ground, just trying washing without shampoo, or just a minimal amount, and see how it works out for you. Vranak (talk) 22:09, 17 April 2010 (UTC)

If you thoroughly rinse and comb your hair under hot-as-you-can-bear running water, you will need noticeably less shampoo to get it clean, so I suppose it is possible that if you did this daily and lived in a reasonable clean environment you might get away without the shampoo altogether. DuncanHill (talk) 23:30, 17 April 2010 (UTC)

We have an article on that: Polish plait. There are people who went their entire lives without ever washing their hair. Ariel. (talk) 02:05, 18 April 2010 (UTC)

I didn't wash my hair for ages out of laziness... No one noticed it, yet at the same time they were horrified to find I hadn't done so. Now that I've started using shampoo again I find my hair does need washing at least once a week. We'll have a massive range of hair flora (like skin flora) that will happily live in our hair and will eat away at all the gunk from our scalp. Washing with shampoo will obliterate them and disrupt the once pristine ecosystem, I'm guessing that it takes time for the balance to return and so soon after washing your hair will be greasy etc. Similarly, I've never washed my face with soap and yet never get spots, meanwhile people who use clearasil all the time seem to always have spots (making them use more clearasil!). Why were you asking? 131.111.30.21 (talk) 11:38, 18 April 2010 (UTC)

Yeah, I go for months at a time without using shampoo as well. I'm not exactly obsessed with my hygiene, but no one's ever complained about my hair smelling. When I don't even rinse it for a week or two, though, it can start to smell. Luckily, that's only when I'm camping, or something, so everyone else is in the same boat. Buddy431 (talk) 17:54, 18 April 2010 (UTC)

Personal Obsevation: acquaintances of mine in the past who stopped washing their hair in order to grow long dreadlocks all asserted that after an initial several-week period of smell, grease and dandruff the scalp's "natural self-cleaning properties" kicked in and thereafter their hair became and remained clean, non-greasy and non-smelly (which indeed it was). 87.81.230.195 (talk) 19:19, 18 April 2010 (UTC)

I was under the impression that the correct (i.e. traditional - I know that you can go to a salon and have dreads done with backcombing and glue) way to grow dreads was 'grow longish, then wash as normal - but never brush/comb it again'. Folks do seem to believe that you have to be black for this to work - but apparently this is not the case. Black peoples' hair tends to dread up quicker, is all. --Kurt Shaped Box (talk) 22:10, 18 April 2010 (UTC)

Article needs help

Hey guys and gals. If any of yall have some spare time, the article on Robbie Mannheim needs some serious help from rational science-minded perspectives. My templates were removed without significant improvement. Finals week is approaching so I don't have the time right now to deal with edit war or doing significant fact checking. It's important to quickly remedy the article because currently it could be damaging WP's credibility. Cheers. -Craig Pemberton 22:42, 17 April 2010 (UTC)

Lol! Yes indeed! I think it's probably best to just delete that whole article and start again.. Send User:Anupam who's responsible for pretty much the whole article to Wikipedia:Reliable_sources. I don't think "Paranormal Experiences", "Strange Magazine", and "Good Spirits, Bad Spirits: How to Distinguish Between Them" count as reliable sources.. Unfortunately I think this requires someone a little more expert then me to tackle it. Vespine (talk) 23:11, 18 April 2010 (UTC)

I might at least put your templates back and start a thread on the talk page. Vespine (talk) 23:47, 18 April 2010 (UTC)

Dandelion-lettuce hybrid?

Earlier in the year I weeded something from my UK garden that had leaves like a dandelion, but was the shape of a lettuce as it had a large number of leaves. What could it have been? I may have scattered some salad-plant leaves there last year. 78.147.241.153 (talk) 22:48, 17 April 2010 (UTC)

It could not have been a dandelion-lettuce hybrid, because no exchange of genetic material occurred. However, lettuce and dandelions are both grouped in the tribe Cichorieae; it is possible there is a species sharing characteristics of both (for example, this). Intelligentsium 23:57, 17 April 2010 (UTC)

Which, though the file is named 'Babcockia', is apparently a species of Sonchus, or "hare lettuce". --ColinFine (talk) 20:45, 18 April 2010 (UTC)

It was really like a hedgehog of dandelion leaves. The dandelions I've seen are quite flat, but this thing was like half a sphere in shape, and also had bigger than usual leaves. It might be due to some old salad plant leaves I scattered there, but I do not know what exactly. 89.240.44.159 (talk) 12:31, 19 April 2010 (UTC)

Is there any realistic danger to Europe from Icelandic Volcanos?

Ok, so at the moment we just have an ash cloud. No big deal. Anything else I should be concerned about, and if so, how concerned? Inquisitive Fellow (talk) 23:09, 17 April 2010 (UTC)

Besides the ash cloud, no. However, the ash cloud is a big deal if you want to travel to or over Europe, as it clogs up airplane engines. And in about a week or two when the ash has circled the Earth we may see much brighter sunsets. --The High Fin Sperm Whale 23:21, 17 April 2010 (UTC)

The article states, "As of April 15, the eruption was not large enough to have an effect on global temperatures like that of Mount Pinatubo and other major past volcanic eruptions. However, previous eruptions of the volcano have lasted as long as a year, and the potential remains for a temporary global cooling effect." 124.157.234.136 (talk) 23:45, 17 April 2010 (UTC)

Depends what you mean by "danger". If it continues it could cause airlines to go bust. It could have a knock on effect on the economies of other countries, because they won't be able to get their goods and services to Europe. Concerts and sporting events are already being cancelled because the players can't get to the venues. Businesses are cancelling meetings and conferences. If and when the ash cloud falls to earth, it could damage people's health. [8] It just proves how interdependent we all are, and how dependent we are on the goodwill of Mother Earth. --TammyMoet (talk) 08:23, 18 April 2010 (UTC)

Without wishing to underestimate the personal inconvenience to people unable to travel this week, I think the overall economic impact will be minimal. UK airlines are estimated to be losing about £2m £200m per day, according to the BBC - but even if this continues for a whole year, it is far less than a tenth of 1% only 2.5% of the UK's GDP. And although airlines are losing money, ferry companies and rail operators are making money. Most goods travel by sea, road and rail, so the only products affected will be those that travel long distances with very short shelf-lives - and a shortage of Thai orchids in Tesco will hardly cause panic buying. As for business meetings, we have phones, video conferencing and net meetings - in my experience, most business travel is a non-essential luxury. Gandalf61 (talk) 09:16, 18 April 2010 (UTC)

On the surface Gandalf you're right. However, cancelling a conference where 600 delegates are attending from across the world costs the organisers money: they will still have to pay for the venue, catering... if you're stranded the other side of the world who's going to do your job? That could bring a business to its knees, especially the smaller ones. Take the F1 circus: 6 jumbo jets to get the freight stuff across the world, plus people, plus spectators... it's not just the commercial airlines here, it's the freight stuff. We could run out of fruit and veg within a week apparently! This article summarises this. The figure they give for airline losses is greater than Gandalf's by 100 times. [9] As you can see from any supermarket shelf, many of the green veg are flown in from Africa or even South America. This will have an effect on their economies as well as our plates in the UK. --TammyMoet (talk) 10:07, 18 April 2010 (UTC)

Hmmm, typically the attendees of a conference will have paid for attending a few months in advance. If the organizers can see the problem happening a few days in advance, they could make last minute arrangements with the catering companies etc. and then be better off. They could then perhaps use the saved money to partially compensate the people who cannot attend. Count Iblis (talk) 13:50, 18 April 2010 (UTC)

Usually there are cancellation clauses in the contract which mean if you cancel less than a set period of time beforehand (could be 48 hours or 7 days) you still have to pay the full fee. Usually the hire fee has to be paid to the venue on booking, which is months if not years in advance, so in order to do what you suggest, you would first have to sue the venue to get even a partial refund. You can cancel the event, but the expenditure is still in place. And what if the flight ban gets lifted and people make the journey, only to find the event has been cancelled and they haven't informed you? (if you're travelling for over 24 hours this is a real possibility) I've organised events for many years, and cancelling is a real nightmare. --TammyMoet (talk) 14:06, 18 April 2010 (UTC)

I see, so you won't want to cancel a conference but perhaps scale it back as best as you can? I've only visted conferences and my experience is that the catering is often poor (under normal circumstances). There isn't enough food for the whole day; after a few days more and more people will eat extra meals in restaurants. So, it seems to me that conference organizers are not spending enough on catering. Count Iblis (talk) 14:26, 18 April 2010 (UTC)

It's poor but very expensive. You are not just paying for the bad food, you are paying for all the people who serve it, for them to put it all away, for them to rent the trucks they need to bring it in and out, assemble tables, etc. Even very minimal food is very expensive, as anyone who has planned a wedding reception knows, much less a full conference with hundreds of people. And since this is an "act of god" (that is, not anybody's fault), it screws up a lot of cancellation policies, insurance policies, etc. Anyway it's beside the point here—aircraft costs are just the tip of the iceberg, because they have an entire sector of the economy depending on their functioning. Shipping of all sorts is mangled by lack of flights; the ability of people to move around is a key aspect of global commerce even today; and there are huge opportunity costs and cancelled service costs which hurts everyone involved. --Mr.98 (talk) 14:38, 18 April 2010 (UTC)

Let's examine some of these exaggerated claims. Cancellation of conferences and sporting events - a headache for organisers, but no net economic impact, as refunds put money back into people's pockets, which they then spend elsewhere. "We could run out of fruit and veg within a week apparently!" - complete nonsense. The UK imports 90% of its fruit and 60% of its vegetables - but only very perishable luxury items are flown in. No-one is going to pay for potatoes or pasta to be air-lifted, are they ? I am sure we can survive without aspargus and fresh pineapple chunks if we have to. "The ability of people to move around is a key aspect of global commerce" - well, yes, but people can still travel by road, rail and sea. And most business travel is simply an excuse to be wined and dined at someone else's expense - I think many companies would actually be more profitable if their staff spent less time on corporate jollies. Gandalf61 (talk) 16:06, 18 April 2010 (UTC)

Why would you assume cancellations have no economic impact? Consider that the companies who you've booked in advance, even in an ideal situation where they've not put out expenses ahead of time that cannot be returned (like food purchases), are now stuck with a weekend worth of labor that they either have to pay for, or there are laborers who thought they'd be getting paid but are now not. In all cases, with insufficient cancellation time, somebody will be out some cost or opportunity cost. There are all sorts of NPR stories about people who ship to Europe from out of Europe being totally screwed, losing entire perishable shipments, etc. All of these things cost significant amounts of money. They are investments that have now gone bad and are probably not covered by insurance. A week's notice is not enough for things to be cancelled or redirected without some economic loss. --Mr.98 (talk) 17:02, 18 April 2010 (UTC)

I'm sure the people who are directly impacted by this are quite heavily inconvenienced (financially, or otherwise) but the impact on the economy of, say, the UK would be negligible. Most air travel is for business and most business air travel isn't necessary for business, in as far as business contributes to the overall economy. Zain Ebrahim (talk) 12:03, 19 April 2010 (UTC)

Would Gandalf be willing to pay for my packet from Germany which has almost definitely been delayed because of the disruption? (Okay I admit it's not going to make an economic impact although having paid a fair amount for the shipping because of Deustche Post/DHL's flatrate (i.e. not by weight) shipping costs I'm rather peeved.) More to the point, plenty of people planning to go to Europe have likely cancelled their holidays. If they have travel insurance policies, they may or may not get most of their money back. But even if they do, it doesn't mean there's no impact because the insurance companies may still lose money and the people themselves may decide to travel elsewhere rather then travel to Europe, which means all the money they would have spent in Europe would go elsewhere, given the details I've mentioned (e.g. insurance), it's clear that 'no net impact' is not accurate but in addition, telling the European businesses and governments who've lost money because it went elsewhere, say Asia or the US, it's okay because there's no net impact may arger them enough to punch you in the face. Back to my earlier point, there are plenty of European sellers of goods who will find people won't be buying stuff. Similar to the earlier case, these people may buy their goods from elsewhere, e.g. Asia or perhaps they'll buy them locally where the good costs more. This will be good for the other sellers of goods but arguing it makes no difference because there's no net impact is just silly particularly if they buy them locally which would probably mean they spent more (otherwise they would have always bought them locally). In the converse example, sellers of goods elsewhere, like on eBay or DealExtreme are likely to find European buyers reduced some may just delay their orders, others may turn to local dealers, again if they're local there's a good chance these items will cost more which while good for the local dealers clearly means 'no net impact' is rather inaccurate. Even a delay of the orders isn't going to mean no net impact. Money the sellers could have received and spent on other things is now not going to be received. It stays around in the buyers back which again may be good for the European banks and therefore economy but as I've already said, there's clear not no net impact. In terms of travel, yes there are other ways to travel, but the people who choose to travel by air much have had a reason, if that reason is speed then the loss of that option is not going to have no impact. Note that even if people travel less, and even if they good for the company, that ignores the impact their non-travel has on other people who would have benefited from their travel. More to the point, less travel doesn't mean positive impact if you have to pay more for the travel that does take place, e.g. because it costs more (flying is generally expensive but it's not always more expensive then other options) or because the person is away for longer. P.S. I'm not particularly sure why Gandalf thinks the Thai orchid growers don't lose out when people don't buy their orchids or if people have already bought their orchids but they can't de delivered, why nothing changes for Tesco because they can't sell the orchids they purchased but which couldn't be delivered. Even if you presume the people still spend all the money they would have spend at Tesco at Tesco which is a big if, they'll be buying more other good which may be beneficial for these sellers of other goods but is not a case of no impact. To summarise, no net impact is clearly silly when there are plenty of loss opportunity costs (I think that's the economics term) and money going to substanially different places including different countries then it would have otherwise. Yes, some will gain, some will lose however there's still a change and the overall effect is clearly going to be negative and even if we take an overall broad view, for most countries the effect is likely to be negative. Perhaps people will realise they're relying too much on air travel and may change as a result which may have a net positive effect but that's a big if. As with others, I've wondered if this could be severe enough to push an airline over the edge, this hasn't happened yet but I've seen some suggestion it could last several weeks, if it does happen I challenge Gandalf to go out and tell the people who lose their jobs if this happens not to worry because there was no net impact. Nil Einne (talk) 23:48, 18 April 2010 (UTC)

If you cancel a conference you have to refund everyone that paid to attend it (whether they would actually be able to make it or not). --Tango (talk) 14:41, 18 April 2010 (UTC)

Incidentally, I am not sure why everyone thinks that conference funds are totally refundable. Many of them will already be spent and non-refundable (you cannot just cancel a huge booking at a hotel and get everything back). When I have been at conferences that were partially cancelled by weather (half of it was called off), I got nothing back. I was told that they might put on the conference again in a few months and then my previous conference ticket would be honored. That would have required twice the amount spent on travel and lodging, though (because my hotel wouldn't refund my costs, of course, because they don't care about the conference). Yes, if you cancel something weeks in advance you can sometimes (but not always) get the money refunded. But in many cases you cannot because you have signed contract of some sort that prohibit this. At least in the US. --Mr.98 (talk) 17:02, 18 April 2010 (UTC)

Back when I was involved in running conferences (or, strictly speaking, conventions) we usually took out insurance against events outside our control causing the event's cancellation. (For those I was involved in, accommodation and conference facilities were mostly provided by the same venue.) Whether or not a natural event like this would be included or excluded (as, say, an "Act of God") would depend on the terms of the particular insurance policy. 87.81.230.195 (talk) 19:12, 18 April 2010 (UTC)

I wouldn´t say the volcanic ash cloud clogs airplane engines. I got the impression that no one wanted to take chances. However, the Dutch airline KLM carried out a test flight Saturday night and detected no problems from the volcanic ash. As far as I know, they flew through the cloud.--Quest09 (talk) 17:18, 18 April 2010 (UTC)

April 18

Vegetarianism and Diabetes

Is there any medical reason a diabetic should not be a vegetarian? A nutritionist told an acquaintance of mine that it's basically impossible for a diabetic to be healthy and satisfied on a vegetarian diet, but I've also heard of a vegetarian diet being recommended to control diabetes. (Please note, I am NOT asking for medical advice here. I'm not diabetic, and I'm a vegetarian for ethical reasons and wouldn't return to eating animal flesh even if I thought my health would benefit by it in some way. This is more of a "settling a bet" kind of question, even though I haven't actually made a bet.) 71.104.119.240 (talk) 02:02, 18 April 2010 (UTC)

Diabetics basically can not properly handle carbohydrates. So it's better for them to get most of their calories from protein instead. This is very very hard to do on a vegetarian (even more so a vegan) diet. The current recommendation is not to cut out carbs totally, but rather to limit them. But anecdotally diabetics who cut carbs almost totally out of their diet do very well. Ariel. (talk) 02:10, 18 April 2010 (UTC)

What Ariel said was unsubstantiated, dangerous and possibly deadly bullshit. Diabetic diets include prescribed amounts of carbohydrate for every meal. Please check with such reliable sources as the American Diabetes Association rather than random persons posting nonsense on the internet. See [10] for instance. Edison (talk) 03:21, 18 April 2010 (UTC)

I said that: "The current recommendation is not to cut out carbs totally, but rather to limit them.". But deadly? Seriously? And despite what the American Diabetes Association says, not everyone agrees, and here is a study that says so. This is not a settled issue though. Ariel. (talk) 04:09, 18 April 2010 (UTC)

discussion about the ethics of vegetarianism

I wasn't aware that there are ethical reasons to be a vegetarian. Dauto (talk) 02:51, 18 April 2010 (UTC) Dauto, Thats a moveable feast. See Vegetarianism and religion. AFAIK ref the OP there is no problem at all with Diabetes and being vegetarian. --BozMo talk 07:34, 18 April 2010 (UTC) I don't know what you mean by moveable feast. Sure, some religions promote vegeterianism, while some other relegions specifically call for non-vegeterian dishes for specific porposes. Fish and lamb come to mind. Some of them forbid specific kinds of meat such as pork or beef without calling for outright vegeterianism. The overall picture is that relegions are all over the place. My question wasn't about relegion though, it was about ethics which is a different thing. Dauto (talk) 14:08, 18 April 2010 (UTC) There is a big difference between religion and ethics (they are related concepts, certainly, but not equivalent). --Tango (talk) 14:45, 18 April 2010 (UTC) Most vegetarians are vegetarian for ethical reasons. They don't think it is ethical to kill animals for food or they don't think it is ethical to treat animals in the way some animals bred for food are treated so don't eat any meat in order to not support the industry or they practise a religion that says it is unethical to eat meat. --Tango (talk) 14:45, 18 April 2010 (UTC) Does that mean that most vegetarians see the meat eaters as a bunch of ethicless people? I rather doubt that. Dauto (talk) 15:56, 18 April 2010 (UTC) Just because it hasn't appeared yet: Ethics of eating meat. Dauto, it would be unfair to call someone who has a different set of ethical principles to oneself "ethicless". 129.234.53.144 (talk) 17:33, 18 April 2010 (UTC) In general it's probably not "ethicless" so much as "ethically challenged". Most vegetarians-for-ethical-reasons in the western world, even militant ones, recognize that there is a large culture and history of meat-eating, so they are likely to believe meat-eaters to be morally ignorant, rather than morally depraved. Most ethics-based pro-vegetarianism campaigns focus on "conscience building" and promoting awareness, rather than moral condemnation. ("You can be a better person" rather than "You are an horrible, evil person.") All this is highly dependent on the vegetarian, though. I've met quite a few who for whom it is a completely personal choice, and who really don't care what others do. -- 174.24.208.192 (talk) 17:48, 18 April 2010 (UTC) Have to agree with 71.104 below, I'm not saying people have to agree with the ethical reasons and I perhaps shouldn't be surprised about a debate about the ethical reasons on the RD even if it's OT, but I'm rather surprised people are seriously unaware plenty of people have ethical reasons (even many of the religious ones have reasons based in ethics even if many religious don't agree with such reasoning) Nil Einne (talk) 10:40, 19 April 2010 (UTC)

25 years ago my first husband became Type 1 Diabetic. He had to inject insulin as well as alter his diet. Being the cook in the family, I well remember this diet! Only 2 portions of red meat a week: change to wholemeal/whole grain products for everything refined (bread, rice, pasta). Plenty of veg. Potatoes with skin on only. No added sugar: very little fat. Been trying to find a reference for this diet, but as it was so long ago I think it's not available. Current NHS advice is that there is no special diet but just to eat healthily: however, the GI or GL diets are well received among the diabetic community. [11] So, is being vegetarian compatible with managing diabetes? It looks like it - providing you still remember to eat healthily! Eating cheese and chips every day is never a good idea (unfortunately). --TammyMoet (talk) 08:13, 18 April 2010 (UTC)

This study (by a vegetarian advocacy group) claims to show vegetarian diets can be quite useful for diabetics. The people in this study were eating a very carefully planned diet though, no chips and cheese I'm sure. Qrsdogg (talk) 13:14, 18 April 2010 (UTC)

Much thanks to those of you who took the time to consider and compose thoughtful responses to the question I asked. As for those of you who felt the need to take the discussion off-topic with what I suspect on the basis of personal experience has more to do with criticism of my moral choices than any actual curiosity about the ethics of vegetarianism (including one individual who felt the need to send a message to me personally) - I only mentioned my ethical stance in order to clarify that I was in no way asking for medical advice by posing this question, as I had no intention of changing my habits no matter what the answer was. Whatever my own private opinions may be, there was nothing judgmental or proselytising about the question I posed; I didn't come here to engage in debate, and I have no interest in doing so. If you must know, though I seriously doubt there's anyone hanging around the Wikipedia reference desk who isn't familiar with the concept that some people don't eat animal flesh for reasons of conscience, Tango and 174.24.208.192 had it about right. 71.104.119.240 (talk) 10:32, 19 April 2010 (UTC)

Sunrise and sunset

In the southern hemisphere (l live in Australia) the day of earliest sunrise is about two weeks before the summer solstice, and the day of latest sunset is about two weeks after the summer solstice. The day of latest sunrise is about eight days after the winter solstice, and the day of earliest sunset is about eight days before the winter solstice. Is it the same in the northern hemisphere, or the opposite? If there is a difference, why? Dolphin (t) 06:04, 18 April 2010 (UTC)

The solar time article, specifically the section on apparent solar time gets at the reasons for this. Around the summer solstice in the Southern hemisphere, each apparent solar day is longer than average, both because because of the tilt of the Earth's axis and because the Earth is near perihelion, which pushes the sunrises and sunsets forward each day. In the winter the apparent solar days are also longer than average because of the tilt of the axis, but tempered by the fact that the Earth is near aphelion so the effect is smaller. In the northern hemisphere the equivalent effect would be that the earliest sunrise would probably be about 8 days before the solstice and and the latest about 2 weeks after the winter solstice (I don't know for sure that the numbers are exactly the same, but I assume so). See also equation of time. Rckrone (talk) 07:29, 18 April 2010 (UTC)

You can ansewer the first part of this yourself here. The World Clock – Time Zones--Aspro (talk) 07:38, 18 April 2010 (UTC)

To add something to what I said before, the degree of this effect is going to depend on your latitude. At latitudes closer to the equator where the length of daylight fluctuates less, the shift in the apparent solar day compared to the official time will dominate more in terms of determining earliest/latest sunrise/sunset, while at farther latitudes the larger fluctuation in length of daylight will put those earliest/latest days closer to the solstices. So those 8 days and 2 weeks numbers would apply only to the northern latitude equivalent to yours. Rckrone (talk) 07:56, 18 April 2010 (UTC)

Yes, it is the same in the northern hemisphere (our earliest sunset is mid-December and our latest sunrise is early January). I puzzled over this apparent asymmetry for about forty years (not continuously!), until I realised that the effect is caused simply by the shift in the time at which the sun is at its highest (local noon), so it is not an asymmetry at all (at least not in the way I had thouhgt). The BBC gives a concise explanation. The effect changes over centuries, but has been this way round since the year 1246. Dbfirs 08:19, 18 April 2010 (UTC)

Concentration of urine

In which part of nephron actual concentration of urine is determined? —Preceding unsigned comment added by Aditya Handargule (talk • contribs) 07:34, 18 April 2010 (UTC)

I don't understand the question, please clarify. StuRat (talk) 13:59, 18 April 2010 (UTC)

Perhaps the questioner can find answers in the articles Nephron, Kidney (Kidney#Osmolality regulation, perhaps?) or Renal physiology -- 174.24.208.192 (talk) 17:26, 18 April 2010 (UTC)

Short answer: collecting ducts alteripse (talk) 18:57, 18 April 2010 (UTC)

enzyme activity

an increase in enzyme activity in a cell is mechanistically due to trascription. this mechanism can be domenstrated by: a)measuring total enzyme acticity in the cell free extract. b)ELISA. c)nothern blot d)western blot. —Preceding unsigned comment added by Pradyumn chauhan (talk • contribs) 10:00, 18 April 2010 (UTC)

We won't do your homework for you. The real point of multiple choice homework questions like this is not to "get the answer", but to make you look up, read about, and understand the concepts involved in the question. I suggest you start with transcription (genetics) and also check out some or all of mRNA, enzyme, ELISA, northern blotting and western blotting. If you have problems understanding any of these pages come back here and we will be glad to help. 131.111.185.69 (talk) 10:58, 18 April 2010 (UTC)

Proposed emergency ash reducing: "Rapid glacier removal operation" off the top of volcano on Iceland.

Goal: Substantially cut down on the international healthcare expenses, in the years to come, stemming from the currently ongoing eruption.

Perhaps a little over-dramatized (but not too much!), one might say that:

The Volcanic ash in the air, is basically microscopically tiny pieces of razor sharp broken glass that is swirling around, all over Europe.

(Hence, neither you nor the Wildlife of the northern hemisphere (which cannot stay indoors keeping the doors shut on bad days), would like to have too much, or any at all, of this in your lungs!).

The ammount of emitted volcanic ash is first and foremost determined by the Volcanic Explosivity Index (VEI) of the volcano in question. (The VEI ranges from "gentle" (VEI=0) to "mega-colossal" (VEI=8)).

The ongoing eruption of the volcano: "Eyjafjallajökull" on Iceland, is currently rated as having a VEI between 0 and 1. (i.e. the ammount of volcanic ash should not be too bad).
But the ash-problem is dramatically exasperated by the meltwater from the Glacier that rests on top of the volcano, because the meltwater flows down into the volcano where it then explosively evaporates. ;-(

Q1: Therefore I wonder, why are not the combined military forces of Iceland, Europe, Russia and North America, trying to mitigate the ash-problem by employing Directed-energy weapons and microwave Masers (so that the glacier could be melted away as if it was ice inside a Microwave oven).
(Some of the pictures in the news seems to show that because of wind in the area, then visibility is good enough! i.e. the target glacier is not covered by smoke that would block enery rays).

Q2: If the above, for some reason, is out of the question then why are they not employing Napalm to do the job?
Even though one, of course, would loose the "surgical precision" of cutting away the ice with the above mentioned "rayguns". Yet, there surely must be more than one heroic and competent icelander that would be willing to walk up there and skillfully place the Napalm by hand! (Of course one would have to be really confident that the result of ones action would be an overall reduction of the waterflow down into the volcano!).

Of course, within a couple of weeks then the volcano itself will have melted a hole in the glacier, but much of that meltwater will have gone down and exploded in the volcano. A few weeks or days of unnecessary intense ash exhaustion ammounts to a big difference!

One might argue that the above mentioned operations would be horribly expensive -- and they would have to act really fast, which will make it even more expensive -- but compared to the saved worldwide expences for healthcare in the years to come, then the cost of a "Rapid glacier removal operation" would be truly negligeble.
--89.9.57.218 (talk) 14:28, 18 April 2010 (UTC)

This may cause bigger problems:

Hooper warned that the eruption may be only a taste of the future if climate change causes ice sheets to melt further. As the last ice age ended, volcanic activity in Iceland increased 30-fold because of reduced pressure on the earth’s mantle.

“Since the 19th century the ice caps in Iceland have been shrinking yet further,” said Hooper. “This will lead to additional magma generation, so we should expect more frequent voluminous eruptions in the future.” Count Iblis (talk) 14:34, 18 April 2010 (UTC) |}

One off-question reply (above) collapsed!
Please remember the How to answer a question guideline at the top of this page! which says: "Keep your answer within the scope of the question as stated.". (The reference desk is not a chat-room). (Well, not quite anyway!).
--89.9.5.27 (talk) 15:04, 18 April 2010 (UTC)

The ash is very high in the atmosphere (that is why it can move so far), we are at the bottom of the atmosphere. While it will eventually fall to earth (and is already doing so in places), the medical concerns are fairly minimal (the only medical advice I saw when ash was falling in Scotland was for asthma sufferers to make sure they had their inhalers with them when going outside, they weren't even advising them to stay indoors). I haven't seen any estimates of the medical cost, but I expect them to be small. The economic cost of suspending all air travel will probably be greater, anyway. Melting the glaciers could cause additional problems that would be worse (increased sea levels, increased eruptions, decreased albedo resulting in greater global warming, etc.). --Tango (talk) 14:51, 18 April 2010 (UTC)

(ec) I think the proposal falls under the category of Geoengineering - using large-scale, technological actions to control earth processes. Two problems emerge: first, it is not clear that any action we can take (including your ice-melting suggestion) would actually mitigate or even impact the danger due to volcanic eruption or ash. Our understanding of the complex interplays between these geophysical phenomena is limited, to say the least. We might even make the situation worse. The second problem is that such actions are very expensive, and it is hard to justify very expensive programs, especially if the results will be uncertain. One issue is that the scale is huge - we would need to expend considerable resources to match the quantity of energy that a volcano can unleash - and those resources might be better used to mitigate the problem in other ways. Nimur (talk) 14:57, 18 April 2010 (UTC)

Hmm...

1. There is no doubt about the fact that water flowing into a volcano will cause dramatic explosions! And thus cause substantially increased ammounts of volcanic ash!
2. The melting of just one small glacier will not be more than a «drop in the ocean» and will have far smaller consequences than all the ash avoided

--89.9.5.27 (talk) 15:16, 18 April 2010 (UTC)

Do you have any idea of the scale of things here? The energy to do what you suggest is enormous. We don't have a directed energy weapon that could melt even a minuscule amount of that ice. And napalm would not do a thing - all the heat goes up, almost none would melt the ice. You would probably need a volcano to melt that much ice :) Ariel. (talk) 15:27, 18 April 2010 (UTC)

That crazy idea doesn't have an icecube in hell chance of working. Dauto (talk) 15:29, 18 April 2010 (UTC)

I ran some numbers, assuming about 300x500x500 meters of ice, you would need 1.501x10^16 joules of energy. Look at Orders_of_magnitude_(energy)#1015 to see how much energy that is - it's about 10 megatons of TNT, i.e. an atom bomb - actually several of them. And even that would not be enough, since most of the energy would be wasted, and sent up into space. Ariel. (talk) 15:38, 18 April 2010 (UTC)

Ah, yes! These are the kind of enlightening replies that I (the OP) was hoping for. Thank you all!
Hmm.. If napalm will not work because most of its heat energy would go upwards...
...Then how about Thermite?
Of course one might need a "few hundred pounds" of it, but one might be able to use it to burn a channel in the glacier, which would divert at least large ammounts of water away from flowing into the volcano. --89.9.5.27 (talk) 15:45, 18 April 2010 (UTC)

A few hundred? While thermite would probably do a good job, and iceland actually produces lots of aluminium, a quick calculation shows that termite can melt about 11 times it's mass in water ice. So 300 pounds of thermite can melt about 36 gallons of water. I don't think that's going to help much. The scale of planetary events is stupendous. Humans don't come close to controlling those quantities of energy. Ariel. (talk)

I have no doubt that if we had solid evidence that melting a glacier would be worth the effort, we could marshal the technology and the resources to do what the OP has suggested (perhaps the most effective technologies would not be napalm or ray-guns, but we could analyze and design an effective method). I disagree with some of the assertions that humans are incapable of controlling that much energy. For perspective, look at what humans are already are capable of. We regularly move mountains; we make the rain start or stop; we control the weather; we generate earthquakes (and control for the natural ones); we split continents in half (actually, we've done this more than once!); we have moved the ocean; we have changed the topology of canyons and filled them up; we have chemically modified our atmosphere many times in many ways; and we harness more energy than a volcano every single day. But all of these things are difficult; they are expensive, they require a huge degree of cooperation, and many times, they have unintended consequences - sometimes the side-effects outlive the original purpose with catastrophic results. The above seemingly-miraculous feats of technology have historically been justifiable, despite the resources necessary. So - while the nay-sayers here are bringing up some valid numbers - and it is totally accurate to say that it would require a huge quantity of prohibitively expensive resources - it all boils down to this. If we decided, with a confidence level beyond a reasonable doubt, that we could make this volcano situation better by melting ice (or any other sort of action), we would take that action, despite its resource-cost. But as of right now, our understanding of the situation is that its effects are actually too small to warrant the sort of massive engineering and economic burden of addressing the situation at the source. It is more efficient to divert aircraft pathways - it is more efficient to accept and plan for (or neglect) any potential global health or climate hazards. All things considered, and even though this volcanic eruption is huge in scale, it is a metaphorical "drop in the bucket" in terms of global resource allocation. It is more effective for us to focus on small expenditures of energy - like dredging the East River to allow super-post-Panamax ships to dock on the East Coast, saving millions of gallons of petroleum that would otherwise be needed to drive freight from a more distant port. So, a tiny project like dredging a river can have trillions of dollars of economic significance; while "de-volcano-izing Iceland" would be extremely expensive with very little direct return (a mere $200 million per day, petty change by comparison). Ultimately, teams of politicians make decisions about which resource expenditures are "cost-effective" - hopefully guided by scientific and engineering analysis. But I think it's unfair to the OP to categorically tell him/her that his idea is "impossible." It's certainly possible - it's just not efficient. Nimur (talk) 16:51, 18 April 2010 (UTC)

A bit of lateral thinking to reduce the resources required: On the equator each square meter receives about 400 watts of the sun's energy per square meter. At the latitudes of Iceland, it might be possible to speed up the melting by reducing this glacier's albedo. This could be done with such things as tons and tons of lamp black or even tons and tones of grey dust. The only problem remaining is where to get enough at such sort notice and how would you cover twenty square miles of glacier with it... Oh! But wait !!!--Aspro (talk) 16:58, 18 April 2010 (UTC)

Perhaps most interesting is that in this era of presumed energy shortage, it is still not cost-effective to harness the immense quantity of freely available geothermal energy that is currently being wasted "melting ice" instead of powering our automobiles and internet data centers. Iceland is ahead of the game, but imagine if they developed the technology to capture and export the volcanic energy, instead of letting it go to waste. I don't know what a volcano-energy-harvester would look like, but I have a sneaking suspicion it would look a lot like this: thousands of tons of very expensive steel structure, tubes, pipes, pumps, and chemical reactors. But why would we waste our efforts harnessing easily-available energy that rose to the surface under its own power, when there is so much energy available many miles below the ocean floor, thousands of miles away from where it is needed? Nimur (talk) 17:04, 18 April 2010 (UTC)

Asexual reproduction

What is the real difference between fragmentation and budding? Is strobilation a form of budding? Or should it be considered a form of larval amplification? Propagule formation is or is not a type of asexual reproduction?

Thanks in advance.--82.55.196.145 (talk) 15:56, 18 April 2010 (UTC)

I think fragmentation happens to the organism, while budding is done by the organism. To me strobilation does not seem to be a form of budding, because the bud is specially made for the purpose, but strobilation is pieces of the entire animal. But all that is just guessing. Ariel. (talk) 17:08, 18 April 2010 (UTC)

... and propagule can be either sexual or asexual, depending on the part used. Dbfirs 20:14, 18 April 2010 (UTC)

Ok, thanks; I imagined the difference was the one suggested by Ariel, but I read that bulbils of Allium are produced through a fragmentation event! Ephyrae are made for the specific porpouse of strobilation and they are not pieces of the animal, but real individuals. I'm a little bit confused.--87.3.123.226 (talk) 11:04, 19 April 2010 (UTC)

iodized salt

how do they add the iodine to salt . do they mix it with powdered iodine or soak it in a liquid iodine solution —Preceding unsigned comment added by Jonny12350 (talk • contribs) 16:05, 18 April 2010 (UTC)

The NY times reference link in our iodised salt article says they spray two ounces of potassium iodate on each ton of salt ... in the Third World. Haven't found yet the process used in the industrialized countries. Comet Tuttle (talk) 16:17, 18 April 2010 (UTC)

Here it is: This page from the "Salt Institute" says, "Modern salt plants routinely spray potassium iodide or potassium iodate onto the salt while it moves along a conveyor belt before it is packaged. In lower-tech operations, iodine is sometimes added as a dry ingredient and physically mixed with the salt." Apparently the US FDA doesn't permit the use of potassium iodate for this purpose, though it's the most common additive globally; so in the US they have to add a couple of additives because otherwise, "Without a stabilizer, potassium iodide is oxidized to iodine and lost by volatilization from the product." Comet Tuttle (talk) 16:30, 18 April 2010 (UTC)

The bit about potassium iodate made me wonder why it's not permitted by the FDA, and this page has some more info if anyone else is curious. That page also has some complaints on the accuracy of the wikipedia article on potassium iodate. Ariel. (talk) 16:52, 18 April 2010 (UTC)

Another discussion of various methods. --jpgordon^{::==( o )} 17:55, 18 April 2010 (UTC)

Wikipedia is the encyclopedia anyone can edit...why didn't they fix what was wrong (or even add a question to the talkpage, so it would get fixed) instead of just complaining off-site? They have two complaints: a cite-needed statement about FDA approval (now removed, because they link an FDA letter to the contrary) and a dosage chart...from WHO which they claim is a bogus-pills vendor? Anyway, back to your regularly-scheduled discussion. DMacks (talk) 03:44, 19 April 2010 (UTC)

Saltwater ecosystems

I am trying to find information on saltwater ecosystems, mainly what animals live in saltwater and what their diets are. Can someone help me out? Thanks, Eagles 24/7 (C) 17:28, 18 April 2010 (UTC)

It helps to know that the ocean is the most common natural salt-water environment - so you can search for life forms that live in the ocean. Invariably, these will be saltwater ecosystems (though some organisms live in both salt- and fresh-water, or brackish environments). Take a look at the "lifeforms" section of our marine biology article to get started; there are hundreds of links within that section alone. There are too many animals in such environments to make a general statement about their diet - each organism fulfills a different ecological niche - but if you can narrow down a little, we can help you find information about specific organisms. For example, baleen whales are marine animals that mostly eat krill. Nimur (talk) 17:51, 18 April 2010 (UTC)

Which, of the millions of species which live in saltwater, are you interested in ? StuRat (talk) 17:52, 18 April 2010 (UTC)

@Nimur: Thanks, I'll go check that out. @StuRat: I'm not really sure which ones I'm looking for, but I'll figure it out. Thanks, Eagles 24/7 (C) 18:02, 18 April 2010 (UTC)

Historical Alternatives to Ballistic Pendulums

Hello. Were there any historical alternatives to ballistic pendulums when finding bullet speed (perhaps shooting a bullet in a tank of water, which would be safer)? Thanks in advance. --Mayfare (talk) 17:29, 18 April 2010 (UTC)

SPARK SHADOWGRAPHS have been in use for a while.[12]. There are also ballistic boxes but I don't know how good they are for working out velocity.[13]--Aspro (talk) 17:56, 18 April 2010 (UTC)

You can perform chemical analysis on the charge to estimate total released energy, but the purpose of such testing is to account for "non-ideal" characteristics. Take a look at ballistics - particularly internal ballistics (although all the various categories are relevant). Some firearm muzzle velocity can be measured with RADAR - especially if the projectile is large (though it can also be applied to smaller munitions). Here's a RADAR to measure ballistics for large artillery. Nimur (talk) 17:55, 18 April 2010 (UTC)

You can measure the speed directly using a high speed camera too. SteveBaker (talk) 21:05, 18 April 2010 (UTC)

ocean currents

why do most of the warm ocean currents flow along east coast while cold currents flow through west coast? —Preceding unsigned comment added by 117.200.67.69 (talk) 17:35, 18 April 2010 (UTC)

Which coasts do you mean ? The US ? StuRat (talk) 17:45, 18 April 2010 (UTC)

The relevant article is boundary current. These processes result from the Coriolis effect. There are some exceptions to the general rule the OP has identified, because geography is complex and ocean currents are affected by many interacting parameters. Nimur (talk) 17:57, 18 April 2010 (UTC)

Coriolis by itself doesn't do it. The main reason is that the ocean's movement is 'forced' by the prevailing winds which are from east to west at the tropics (trade winds) and from west to east at temperate latitudes (westerlies). Dauto (talk) 18:39, 18 April 2010 (UTC)

True, but Coriolis is responsible for the lateral components of both trade winds and westerlies. Dbfirs 20:08, 18 April 2010 (UTC)

bond formation of SiO

what type of bonds involve in SiO(Silicon mono oxide).If they are different to CO (Carbon Mono Oxide ) plz give explaination.--True path finder (talk) 19:57, 18 April 2010 (UTC)

I would expect they are the same as carbon monoxide (CO): One O⁺ with a triple bond to a C^-. --The High Fin Sperm Whale 21:11, 18 April 2010 (UTC)

single crystal chalk (kitchen chemistry woohoo!)

My friend wants to know if powdered chalk can reconstituted into more solid chunks of chalk. (It's magnesium carbonate.) It's basically for more convenient handling as gymnasium weights, rather than any sort of blackboard-writing. My current plan is to dissolve the chalk in boiling vinegar, and then slowly distill it over a long period (an hour?). Will this work? John Riemann Soong (talk) 21:31, 18 April 2010 (UTC)

Do you mean chalk, gypsum or magnesium carbonate? The stuff you write on blackboards with, despite the common name, is gypsum. Neither gypsum or chalk is magnesium carbonate. Chalk is calcium carbonate and gypsum is calcium sulfate dihydrate. I'm not sure any of them will dissolve in vinegar. They will react with it and become some other compound, so distillation wouldn't get it back. To get it to form a large crystal you probably have to heat it up a lot until it melts (probably without exposing it to oxygen, or anything else it might react with, in the process) and then cool it slowly. (The melting point of chalk is 825°C, so not easy to reach.) --Tango (talk) 22:04, 18 April 2010 (UTC)

{ec}You will decompose it to magnesium acetate, and carbon dioxide will escape. You may be able to crystalise that salt however and then carve it into a weight, as it will not be very hard. However don't expect it to be too strong either! It is likely to be brittle. You will need a lot of vinegar to do this. Tens of liters. Melting it will not be a kitchen capability. It is easier to melt lead or solder in the kitchen if you want to make weights. Graeme Bartlett (talk) 22:07, 18 April 2010 (UTC)

The "chalk" I usually see in gyms and billiard-halls is more of a compressed chunk of powder rather than a single crystal. A single crystal would probably be hard, have a clean geometric shape, and be translucent/transparent rather than an amorphous powdery opaque blob. DMacks (talk) 22:16, 18 April 2010 (UTC)

Well I meant gymnasium chalk MgCO3. AFAIK I would get magnesium bicarbonate if I dissolve at a low pH, which is water soluble. I also expect boiling water to help me dissolve the rest. Completely protonating magnesium carbonate to carbonic acid + magnesium acetate is likely to be difficult, naturally. John Riemann Soong (talk) 00:40, 19 April 2010 (UTC)

magnesium bicarbonate is not very stable and you really need to have a high pressure of carbondioxide to counter the decomposition. Heat would help the decomposition by boiling off carbon dioxide, and you are more likely to get a crust forming than a single crystal. Graeme Bartlett (talk) 09:08, 19 April 2010 (UTC)

If all you need is weights, why not just mix it with a small amount of glue? And why chalk for weights anyway? I can think of lots of other materials that might be better. Ariel. (talk) 09:15, 19 April 2010 (UTC)

April 19

Rain will clear the skies of ash, but can we artificially fill up the water by nuclear power?

1. Many submarines and some large ships use nuclear reactors for propulsion, and for all of their energy needs.
   If one of them were to anchor up off the coast of Iceland and, running its nuclear reactor on "full steam" (pun intended), used all the heat energy available, then how much sea water could theoretically be evaporated per 24 hours?
2. Nuclear power plants often use seawater for cooling.
   If one of the power plants on the coast of Europe were to be solely employed to evaporate water, then how well would it do per 24 hours?

All I have heard about rain-making, earlier, is the Cloud seeding, but at least that part of the job is allready well and surely taken care of by the volcano Eyjafjallajökull on Iceland. Now, if only we could get some millions of Cubic metre of extra water up in the skies, to soak the volcanic ash...
--Seren-dipper (talk) 00:16, 19 April 2010 (UTC)

It would be insignificant. Even if you could get together a gigawatt of electricity generation to devote to evaporating water (and that corresponds to several nuclear power plants) it would only be equivalent to the energy from the sun on about 4 square kilometres of ocean (can someone check my arithmetic?). The sun is so much more powerful than anything we can create that there is really no point us trying to help it along. --Tango (talk) 00:26, 19 April 2010 (UTC)

That's correct. it would be completely insignificant. Besides, lack of humidity in the air is not the limiting factor that prevents rain. Atmospheric lift is the main controlling factor. BTW cloud seeding doesn't work either. Dauto (talk) 01:27, 19 April 2010 (UTC)

I question the accuracy of the last statement. Yes the state of research is rather poor, it's difficult to prove what would have happened if you hadn't seeded and and many of those who use or promote it don't have good evidence it works (and personally I expect it doesn't work as well as many of them may like) however

Cloud seeding has been shown to be effective in altering cloud structure and size and in converting supercooled liquid water to ice particles. The amount of precipitation due to seeding is difficult to quantify. Cloud seeding may also suppress precipitation.[citation needed]

Overall, there is general expectation that winter cloud seeding over mountains will produce snow, expressed by professional organizations.[1][2][3][4] There is statistical evidence for seasonal precipitation increases of about 10% with winter seeding.[5] The World Meteorological Organization has indicated that cloud seeding produces positive results in many cases but is dependent on many factors such as specificity of clouds, wind speed and direction, and terrain.

These don't exactly suggest it doesn't work (which I take to mean there's strong evidence it hardly ever or even never works). Also:

A 2003 study[23] by the United States National Academy of Sciences urges a national research program to clear up remaining questions about weather modification's efficacy and practice.

Which while not saying it works, hardly suggests the NAS thinks it's a clear cut case with strong evidence it never works.

As I mentioned there are plenty of people, particularly developing countries who use cloud seeding and while I would agree many of them don't appear to have undertaken research or otherwise have good evidence they're doing anything useful, some of this does take place in developed, democractic countries where there's perhaps lesser ability for completely useless programmes to be undertaken and usually some requirement for evidence for such programmes. (None of this means they're immune to carrying out nearly useless programmes with little evidence to support the benefit.) E.g.

In Australia, CSIRO’s activities in Tasmania in the 1960s were successful[citation needed]. Seeding over the Hydro-Electricity Commission catchment area on the Central Plateau achieved rainfall increases as high as 30% in autumn. The Tasmanian experiments were so successful that the Commission has regularly undertaken seeding ever since in mountainous parts of the State.

While uncited, it's easy to find evidence this programme continues in Australia [14]. Some of the latest research I could find [15] (PRs [16] [17])

The Chinese do do their own research although a lot of it isn't published in peer reviewed scientific journals (or at least recognised ones) unfortunately so many would feel it's next to useless, but e.g. [18] [19] [20]

Note that even if the effect is small that many would feel it's not cost effective, or it simply changes the place or time of rainfall, or is otherwise useless for many of the purposes it's advocated and used for, this doesn't mean it doesn't work per se.

Recently of course, various geo-engineering suggestions to reduce global warming, including cloud seeding are being consider, albeit not generally to produce or reduce precipitation, e.g. [21]

Nil Einne (talk) 09:17, 19 April 2010 (UTC)

I certainly don't see how it could help. When you look at those impressive photos of the volcano (this one, in particular) the white stuff coming out of the top is steam (well, water vapor) - the dark stuff is the ash. As you can see, there is already a lot more steam than ash - and the steam isn't winning! SteveBaker (talk) 01:51, 19 April 2010 (UTC)

Surely all the ash is way above the height that generates rainfall. —Preceding unsigned comment added by 86.4.186.107 (talk) 05:48, 19 April 2010 (UTC)

use for nuclear waste

What articles cover using the heat generated by nuclear waste to boil water after the nuclear waste is processed by "freezing" it into ceramic or glass marbles to fill up a tank through which water is passed? 71.100.1.71 (talk) 03:45, 19 April 2010 (UTC)

I don't think there is an article. The heat given of by wast is thought of as 'low grade' heat. In economic terms, the capital investment for the plant, machinery and maintenance, that would be need to utilize this low grade heat for something, would be more than the cost of using other energy sources. In other words, with current technology, it is not worth the effort.--Aspro (talk) 08:17, 19 April 2010 (UTC)

The OP correctly spelled "waste". Cuddlyable3 (talk) 08:51, 19 April 2010 (UTC)

This article: Nuclear reprocessing. Instead of using the heat directly, the parts of the waste that still contain usable energy are separated from the ashes, and then reused. The article should also give you links to reactors that are able to burn uranium down to basically nothing, with almost no leftover (radioactive) waste at all. The article should also talk about the pros and cons of doing so. Ariel. (talk) 09:12, 19 April 2010 (UTC)

ISS framework overbuilt?

I see that the backbone of the International Space Station weighs 147 tons on earth. Given the weightless environment of orbit, what need is there for such strength?Bobstuart (talk) 03:55, 19 April 2010 (UTC)

Spacecraft weigh a lot for a variety of reasons. The ISS is manned, so it must be pressurized - therefore, it must be built to withstand the pressure gradient between its interior and the vacuum outside. Also, the modules must be structurally supported, so there is a need for some quantity of material to connect the pieces. Finally, keep in mind that the space station components must be built on the ground (in "1-G") and survive a very vigorous shaking during launch (possibly subject to serious vibrations and accelerations). The structure has to withstand all of these conditions. In any case, I think you might underestimate just how much materials actually weigh (rather, how much mass they have). All told, 150 tons is not a whole lot of material; you might try to compare the mass of a similar-sized office-building on Earth. I've seen estimates for the mass of a house averaging out to about one to two tons per square-foot of occupied area (of course, the mass isn't uniformly distributed, with more mass in the walls than on empty floor); so the ISS weighs about as much as a small corner of your kitchen! Considering its habitable volume, it's actually pretty light. You might also want to try comparing it to an aircraft. A top-of-the-line single seat F-35 has a takeoff weight of about 30 tons - again, the ISS is pretty darned light, considering that it houses around six people "comfortably" - living areas, bathroom, work areas, laboratory, and exercise facility! Nimur (talk) 05:18, 19 April 2010 (UTC)

First, it's vanishingly unlikely that it is overbuilt: given the cost of lofting mass into orbit, you can be reasonably sure that the rocket scientists pared the weight to the bone. Somewhat per Nimur's answer, you're perhaps confusing weightless with massless. As & when the ISS' position is moved, the structural components need to get all of the mass to move in lockstep; weight is not very relevant. Mass is, and needs a structure sufficient to enable all components to accelerate and then decelerate without coming to pieces. --Tagishsimon (talk) 10:20, 19 April 2010 (UTC)

sperm for Iceland

Seriously, for those not in the know. Icelanders want diversity in there population due to many inherited genetic flaws. Is there somewhere I can get more information on this and find possibly a contact through which I can donate my sperm? 71.100.1.71 (talk) 03:56, 19 April 2010 (UTC)

Maybe they prefer some who can spell "their"?--Lgriot (talk) 07:39, 19 April 2010 (UTC)

Here is a link to the Iceland Directorate of Health, which could provide some leads. Ghmyrtle (talk) 08:10, 19 April 2010 (UTC)

You must clearly specify whether your donation will be in U.S. or Imperial gallons which are 3.785 or 4.546 liters respectively. Cuddlyable3 (talk) 09:13, 19 April 2010 (UTC)

Are you trying to be BB? The OP didn't suggest anything about donating gallons of material. Maybe the intend to donate in litres? Or more likely in samples which I suspect (somewhat supported by Sperm donation) is the normal way sperm banks take donations. (The samples then being divided into seperate vials, the number depending on sample volume and practice of the sperm bank.) Or they're flexible and would donate in whatever units the Icelandic authorities want? Nil Einne (talk) 10:23, 19 April 2010 (UTC)

Iceland enjoyed massive injections of Anglo-American sperm during the Second World War. DuncanHill (talk) 10:41, 19 April 2010 (UTC)

"Enjoyed" you say? I'd like to see a reference to back up that claim.--Rallette (talk) 12:06, 19 April 2010 (UTC)

how do you cite the wistful look on an old lady's face as she recalls the young men who used to pop round for a helping of puffin? DuncanHill (talk) 12:13, 19 April 2010 (UTC)

Indeed. The things that lie concealed behind the formulaic "personal communication with author".--Rallette (talk) 12:20, 19 April 2010 (UTC)

being really happy ==> more brain damage?

What prevents dopamine neurotoxicity from being a problem in "naturally happy" people? For example, the intense rushes induced by naturally-produced beta-endorphins and runner's high? John Riemann Soong (talk) 04:08, 19 April 2010 (UTC)

My understanding is that dopamine neurotoxicity requires concentrations massively higher than could be achieved naturally -- it requires drugs, in other words. Also endorphins, which are related to opium, having a considerably stronger effect of suppressing the pain/suffering system than of activating the dopamine-dependent reward system. Looie496 (talk) 06:02, 19 April 2010 (UTC)

Yes, but it's possible to be really high while on an endorphin rush, to the extent that I will attest to its greater potency over alcohol or even methamphetamine. Which makes me wonder about the neurotoxicity of "natural" endorphin rushes (in general, not asking for medical advice). I know that if you combine physical exertion with a socially intense situation (like a party) the rush can be mind-blowing. John Riemann Soong (talk) 06:19, 19 April 2010 (UTC)

There are different kinds of "naturally happy" people. Some people go "happy" and benign after a stroke kills off some of their brain (and some do the opposite). I would not assume a naturally happy person has higher dopamine. --BozMo talk 09:29, 19 April 2010 (UTC)

Arterial injuries

Before I ask I should say that this is not a request for medical advice. I am not asking what one should do in the situation described, merely what medical opinion holds the prospects to be. I should also say that trying to picture this is not for the squeamish, but here goes. The article on blood squirt says that in the case of carotid arteries, "a completely severed artery will spurt blood for about 30 seconds and the blood isn't going to spurt much higher than the human head. If the artery is just nicked, on the other hand, the blood will spurt longer but will be coming out under pressure and spraying much further." If a person suffers an injury such that blood is squirting out of them under pressure like this, is there any hope for them? The mere thirty seconds until enough blood is lost that it no longer spurts suggests not to me, in the case of full severance, but I'm interested in the second scenario described in that quote. I suppose what I'm asking is whether blood can possibly clot under such high-pressure conditions, or whether applying pressure to a wound like that could possibly stem the flow. I suspect that in an operating theatre something could be done but I struggle to imagine how any victim of an injury to a major artery outside of such a favourable setting could do anything to save themselves. Am I right? Thanks in advance. — Trilobite 05:06, 19 April 2010 (UTC)

No severed major artery can clot fast enough to prevent death by exsanguination, but exsanguination can often be prevented by pressure on the wound in all major peripheral arteries, including the lower aorta. The carotids and upper aorta are a special case because the blood supply to half the brain would be immediately terminated even if pressure is applied to stop the bleeding. alteripse (talk) 10:54, 19 April 2010 (UTC)

can combine theory

DEAR SIR, GOOD DAY TO YOU.I WANT TO KNOW ABOUT SUPER STRING THEORY CAN COMBINE DNA STRUCTURE? NUCLEAR FUSION CAN COMBINE QUANTUM THEORY? PLEASE REPLY ME.THANK YOU. KOKOGYI,BURMA —Preceding unsigned comment added by 203.81.72.200 (talk) 05:53, 19 April 2010 (UTC)

First, please don't type in all caps; it is unpleasant to read. Anyway, what do you mean by "combine"? Someguy1221 (talk) 06:08, 19 April 2010 (UTC)

There can be very few connections between DNA structure and super-string theory. They are not at all the same sort of string!

Quantum mechanics does have some bearing on Nuclear fusion, but it is not essential for the basic theory.

Read our articles (linked above) for more information. I suppose that quantum theory could include nuclear fusion in its predictions, and super-strings are supposed to explain the whole universe, but they haven't got very far! Dbfirs 11:57, 19 April 2010 (UTC)

Test for swelling in knee joint

I vaguely remember a clever test for swelling in the knee, which involved the patient sitting with legs extended and the practitioner stroking the knee joint to empty it of fluid and then stroking it once more, in order for it to "fill up" again, if any swelling is indeed present.

I've tried Googling for it, but so far without joy. Can anyone point me in the right direction?

And no, this is not a request for medical advice, I'm not planning on using any information gained for diagnosis etc just assuaging curiosity. --Dweller (talk) 10:04, 19 April 2010 (UTC)

Air Conditioning

is it true that split air conditioners are not capable of taking fresh air i.e. whether it recirculates the same air? if so the oxygen content will decrease in the room. 203.199.205.25 (talk) 10:21, 19 April 2010 (UTC)

This is not normally a problem when there are windows and doors to provide some air circulation, but in an overcrowded or sealed building there might be a build-up of carbon dioxide and a lack of oxygen even when the air conditioner is blowing cold air. Most countries have regulations about air changes per hour in buildings. Photosynthesising plants can help to restore the balance, but opening a window is usually more effective. Dbfirs 12:21, 19 April 2010 (UTC)

Circadian rhythm abnormalities in non-humans?

I recently discovered that I have delayed sleep phase syndrome, i.e. that my mind and body are biologically programmed to be most alert in the evenings and late at night and to crave sleep in the morning. I find myself wondering if natural circadian rhythm abnormalities have been observed in any other species. Does it ever happen that a member of a generally nocturnal species simply can't sleep during the day and can't stay alert at night? Or do diurnal non-human animals ever have a condition like mine? I know that species-atypical behavior is in most cases likely to get an animal in the wild killed, but has this ever been observed of animals in captivity (as the animal's natural behavior, not the result of any kind of human manipulation)? 71.104.119.240 (talk) 10:42, 19 April 2010 (UTC)

Think. You seem to be asking if a member of another species went to a doctor and complained of symptoms indicating that its sleep/activity cycle was out of synch with its peers. Or are you asking whether veterinarians ever make a diagnosis of delayed sleep phase in pets or farm or zoo animals? Or whether ethologists watching wild animals have ever diagnosed one as having an abnormal sleep cycle? Or whether the circadian rhythm pattern of a whole species fails to match some external standard derived from other species? alteripse (talk) 10:48, 19 April 2010 (UTC)

Greenwich meridian.

Why does not the 0 deg meridian(WGS-84) pass through the Greenwich meridian?Or otherwise why is not the 0 deg meridian in WGS-84 chosen to pass through the Greenwich meridian? —Preceding unsigned comment added by 116.90.224.116 (talk) 11:14, 19 April 2010 (UTC)

You will find it explained here.--Rallette (talk) 11:54, 19 April 2010 (UTC)

Basically, an accidental difference, and since the choice is arbitrary, and the difference is only five and a half seconds of arc, it has not been necessary to standardize. Also, because of drifting tectonic plates, exact longitudes are impossible over decades or centuries. Dbfirs 12:09, 19 April 2010 (UTC)

How much ash to stop a car?

If the amount of volcanic ash kept increasing, which would be the first to stop operating - humans or cars? Thanks 89.240.44.159 (talk) 12:26, 19 April 2010 (UTC)