Wikipedia:Reference desk/Archives/Science/2011 January 12

= January 12 =

Obesity and diabetes caused by low carb diet?
There are so many more obese people in North America compared to Europe that you can instantly see the difference on the streets. Also, when I'm in the US or Canada, I have difficulties getting my usual high carb, low fat diet. If you order steak with potatoes, what you get is a huge steak and hardly any potatoes. Ham sandwich for lunch? You'll get a lot of ham, hardly any sandwich, like this. Apparently, this is the normal North-American diet, they get most of the calories from fat, proteins, and eat very little carbohydrates. Also, people there seem to think that carbohydrates are bad. After first ordering for more potatoes, I only got what I was served the first time, so I asked for a plate full of potatoes. The (very obese) waiter almost refused to give me that. He said that it is very unhealthy to eat that many potatoes, even though one plate full would still be half of what I normally eat. After finishing that plate I ordered another plate. The waiter almost went crazy...

This leads me to think that a normal high carb diet can prevent obesity and diabetes. Perhaps people in North America are obese because they believe that carbs are to blame for obesity. So, the less carbs they eat, the fatter they become, prompting them to eat even less carbs. This makes sense, because a low carb diet will give you very little energy to be physically active. Energy from fat cannot be released rapidly enough to sustain activities like fast running for long... Count Iblis (talk) 00:54, 12 January 2011 (UTC)


 * Wow - I had exactly the opposite observation - that people in the US eat way too many carbs, and not enough fats, and that is causing the obesity. (Since fats make you feel full.) I think you just had a weird waiter. Also Americans eat a lot of cereal (breakfast cereal). Ariel. (talk) 02:10, 12 January 2011 (UTC)
 * Bulk makes you feel full, not carbs or fats per se. 71.198.176.22 (talk) 06:41, 12 January 2011 (UTC)
 * Not true. How full or empty your stomach is is only one way your body controls Hunger_(motivational_state) (I wish that article were better). People with no or little food often try to fill up with non-nutritious bulk, but such accounts also record how hungry they continued to be. 86.163.214.50 (talk) 09:13, 12 January 2011 (UTC)
 * I think 71 is correct, bulk and weight provide feelings of satiety. The hunger article seems to be about how you feel after not eating for 12 hours or more, not about satiety. See http://www.mendosa.com/satiety.htm and http://nutritiondata.self.com/topics/fullness-factor - interesting graph if you scroll down. Regarding carbohydrates: those containing more fibre help make you feel full for longer, not the refined ones. According to this http://www.ncbi.nlm.nih.gov/pubmed/7498104, a lot of fat (as in the stereotypical American diet) induces people to over-eat. 92.24.181.36 (talk) 13:02, 12 January 2011 (UTC)
 * The phrase "Standard American Diet" (a somewhat derogatory term) is sometimes used to refer to a diet that is both high in fats and high in processed sugars (e.g. cola, candy, added sugar). It is correlated with various diseases and obesity. Overall though, the more important predictor of obesity is chronic overeating, i.e. eating more calories than your body actually needs. Some foods, including both fatty foods and high carbohydrate foods, have a high level of Calories per unit volume, which can make them easier to overeat (as compared to most fruits and vegetables, for example). However, that's certainly not the only factor. Cultural factors, such as a preference for snacking and large portions, also contribute to overeating. At the same time there is a lot of contradictory diet advice. For example, the Atkins diet (a rather popular fad diet in American a few years ago) recommended that people would best lose weight on a diet very low in carbs and high in fats. On the other hand, the food guide pyramid and other standard advice tends to recommend a low-fat diet with carbohydrates as the dominant base. Dragons flight (talk) 02:38, 12 January 2011 (UTC)


 * The matter is almost certainly too complex to be reduced to a three-way fat/protein/carbohydrate split, let alone to a hypothesis that any of the extremes in that simplified continuum is ideal. Each of the three groups contains wild variability in digestability, metabolism and biologic utilization. For example, there is a huge difference between how a given amount of "carbohydrates" affect the metabolic regulation when eaten as readily-dissolved simple sugars, or as slowly digested long-chain starchy food.
 * The energy breakdown also says nothing about fiber, or any of a long list of trace nutrients, or even currently-assumed-irrelevant compounds that have yet undiscovered effects on appetite regulation and metabolic signalling. –Henning Makholm (talk) 02:53, 12 January 2011 (UTC)

http://equalitytrust.org says it's due to income inequality: people who don't know how they will make their next housing or heating payment are more likely to overeat from the abundant subsidized high calorie food sources available in the US. 71.198.176.22 (talk) 06:41, 12 January 2011 (UTC)


 * I believe Europeans eat more vegetables and fruit, and less meat, than in the US. For example http://www.bmj.com/content/338/bmj.b2337.abstract?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=mediterranean&searchid=1&FIRSTINDEX=0&sortspec=date&resourcetype=HWCIT And see the links regarding satiety above, including a report that says that fatty food makes people over-eat. 92.24.181.36 (talk) 12:29, 12 January 2011 (UTC)

Thanks everyone for their responses. I still think there has to be a simple difference between Europe and the US and Canada, simply because the difference is so huge. One other thing I noticed was that in North America you also have many extremely obese children. Then, I've read that the weight of adults is relatively independent of diet, it depends more strongly on the number of fat cells you have, because the body is programmed to modulate the metabolic rate so as to keep the fat cells filled to some fixed degree. So, if you eat too much as a child and grow up to become an obese adult, you are unlikely to ever get a normal weight. A BBC horizon documentary demonstrated this by putting volunteers on a 5,000 kcal diet for a few weeks. Most participants only gained a modest amount of weight and all returned to their old weight after the experiment withing a few weeks. So, perhaps US parents give their children too much to eat? Count Iblis (talk) 00:15, 14 January 2011 (UTC)
 * McDonalds is hardly health food. From my experience in observing obese people buying foods in a supermarket etc, they buy a lot of highly processed fatty food which, as mentioned above, makes people over eat. And they buy lots of it. So I imagine the kids get fed a lot of food containing high amounts of fat, and not much fruit and veg or fibre. 92.15.24.16 (talk) 13:59, 15 January 2011 (UTC)
 * Heart Attack Grill :)  . Count Iblis (talk) 02:08, 16 January 2011 (UTC)

Something aliens do on TV that I wonder if it's true
I saw a Doctor Who episode where aliens made all the TV channels, radios, and phones broadcast specific message and I'm wondering if this is real or fiction. I've noticed that things like iPhones (especially original ("2G")) causes radio frequency interference when it gets near speakers where the speakers buzz and such. So I'm wondering about the idea of something that causes that kind of interference that you point it at a speaker but instead of just random noise, it'll send out say music and the speaker plays music. I'm not talking about jamming radio signals as on TV/radio as that's been done before, but where any speaker will pick the sound up as long as it's not shielded and has power to it. Geoffry Nathan (talk) 02:54, 12 January 2011 (UTC)
 * It is quite possible to get a simple radio to broadcast a message accross a broad range of frequencies. If you've ever been VERY close to a transmitter, you will sometimes find that the station being transmitted will "bleed" through and show up over the entire dial.  What basically happens is that a very high powered signal will bypass the tuning circuit and just drive the radio by itself.  The principle is actually explained here, which describes how to build a working AM radio receiver without a tuning circuit or even an external power source.  -- Jayron  32  03:25, 12 January 2011 (UTC)
 * You can broadcast all frequencies at once, but it won't work. AM has one modulation scheme, FM another, cordless phones a couple more (some digital some analog), TV also has video, and cell phones are packet based and you couldn't send to all at once even if you wanted to. And then you have PAL vs NTSC differences for TV, and the same frequencies in different parts of the world is used by different devices, and basically you have to individually target each type of receiver. Ariel. (talk) 04:35, 12 January 2011 (UTC)
 * You're talking about aliens traveling across the galaxy and then saying that they can't do something?  Dismas |(talk) 04:52, 12 January 2011 (UTC)
 * Sure - just being able to travel the galaxy isn't really that hard if you have time to space - photons do it all the time, and they're not very smart. Radio is radio, there is no reason to think aliens have any special abilities with it. If they want to target all receivers they'd need to design for each type. Ariel. (talk) 06:51, 12 January 2011 (UTC)
 * Dismas's point aside, it is perfectly possible to broadcast a signal so powerful that you can essentially bypass the tuner of a radio and cause the signal to "appear" to be coming from all frequencies. This works equally well for FM receivers as AM receivers (you'd need to broadcasting both FM and AM signals to be picked up by both).  My cheap clock radio which plays the local FM country station at all frequencies (said tower is about 3 miles from my house) will attest to that.  Analog TV signals are an order of magnitude more complicated than radio, but in principle if you use the correct standards you should be able to hijack it in much the same method (i.e. broadcasting a powerful enough TV signal, correctly coded, could possibly bypass the tuner circuit as well).  With Digital TV, such methods likely wouldn't work, neither with Cable, so we'd have to fall back on "Any species intelligent enough to traverse interstellar space could figure out how to do it" response.  -- Jayron  32  04:59, 12 January 2011 (UTC)
 * I do not believe any intelligent life form (human or otherwise) could decipher, intercept, and then overpower all forms of human telecommunication on Earth, without having significant a priori knowledge of our communication technology. I have played with radio telecommunications as a professional and as a hobbyist, and I will comment that the modern standard telecom systems are really complex - far more complex than the old AM radios that existed a hundred years ago.  It's doubtful even a skilled engineer who knew what to look for in an intercepted satellite-TV signal could decipher and reverse engineer the MPEG-2 transport scheme with interleaved coding digitally modulated on to a phase shift keyed left-hand polarized S-band link.  And that engineer might have been specifically trained to know what all of those techniques are, what RF and digital parameters are used, and how they are conventionally applied in industry!  Imagine trying to reverse-engineer technology invented by another species!  Unlike old-fashioned AM radio, having one parameter or one circuit out of sync will mean the difference between perfect signal reconstruction and no signal at all.  (Try soldering in one single transistor in the wrong place in a Satellite Television receiver, for example, and see if your signal only "degrades slightly"!)  This says nothing of link encryption or other methods that are presently used to actively obfuscate the signal! Sure, an intelligent human can scan the RF spectrum and determine that non-random information is being transferred.  And they might even be able to estimate, by bandwidth analysis, that the signal contains video data or audio data.  But it's very unlikely they could reverse-engineer / decipher it if they didn't have all the standards, specifications, electronic circuits, digital decoders, and software stacks, that now make up modern telecom systems.  When SETI looks for intelligently-created extraterrestrial signals, they really focus their efforts on seeking out alien life that wants their signal to be understood - nice, slow, repetitive broadcasts of simple, low-entropy information that would be encoded in a straightfoward way.  Even when we put video signals on the Voyager Golden Record, we used analog encoding, a mechanical transport medium, and included instructions.  Yet most SETI experts consider it essentially impossible that an extraterrestrial life form could ever play back that video-phonograph, even if it was neatly packaged and handed to them.  (Truthfully, that record is really more of a tongue-in-cheek artistic statement by Sagan et al. on the impossibly unlikely level of technological complexity that 1970s humanity had already achieved, more than it is an effort to communicate with anyone).  Most importantly, the Golden Record makes the assumption that an intelligent lifeform will have eyes and thus will care about our encoded video signal.  In the reciprocal case, when hypothetical aliens come to Earth and detect all this spurious nitrous oxide in our atmosphere, it is equally likely that they will spend millenia in their advanced universities trying to decipher the complicated ways we periodically chemically modulate our atmosphere in an effort to communicate with us; they very well may not use electromagnetic signaling at all, and never even look for our radio transmissions.  Nimur (talk) 19:34, 12 January 2011 (UTC)
 * Mere Earthly hackers many times took over TV and radio broadcasts. In one type of piracy, they transmitted their own microwave signal to the transmitter site of 50000 watt clear channel AM stations and sent their own program over it for a while. In another type of hack. A hacker disguised as "Max Headroom"  sent his own satellite uplink signal and took over the TV programming being relayed by the satellite, interrupting a football telecast. Then he  even interrupted Dr Who!!!!. Hacker "Captain Midnight" pirated the HBO satellite. It should be trivial for technology equivalent to Scottie on the Enterprise if they visited a planet with 21st century Earth technology. If they have the power and technology to travel swiftly across the universe, then they might take the message from Their Leader and transmit it from drone aircraft over each city on all the local AM, FM and TV frequencies at a power level many dB higher than the local transmitters, in a bruit force takeover. Maybe they have amplifiers which work from DC to light and they just send out an overpowering signal. For phones, they could send little robots to all the phone exchanges and celphone repeaters to ring all phones and transmit their message. That leaves voice over internet. They would be thwarted, because their software would run into undocumented features of the internet infrastructure, then they would get stuck on the phone talking to useless drone tech support folks who would step them through ineffective and timewasting  scripts. 21:13, 12 January 2011 (UTC)Edison (talk)

On a completely random note, something very interesting happened to me when I was young. I plugged both my TV and Nintendo into the same outlet, but realized I didn't have a cable to connect the two. Oddly, however, the TV nonetheless showed the faint analog signal coming from my Nintendo; evidently, it was traveling through the electrical circuit. As such, I suppose, the aliens might be very good at broadcasting to analog (though not digital) devices, although at such breathtakingly high energy levels that it might blow out the Earth's power grid. Magog the Ogre (talk) 19:17, 13 January 2011 (UTC)
 * When I lived in the same building as an FM radio transmitter, I didn't even need a tuner. If I turned on my speakers, I could hear the radio playing faintly through them (I assume that the input wire was acting as an antenna). Paul (Stansifer) 16:13, 14 January 2011 (UTC)

Also, Edison, I laughed. Magog the Ogre (talk) 19:25, 13 January 2011 (UTC)

Which Animal has the biggest brain?
Which animal has the biggest brain? 174.114.236.41 (talk) 05:52, 12 January 2011 (UTC)


 * I'm pretty sure it is the blue whale. Joey williams with a 19 foot long blue whale skull.jpg The skull shown in the pic to the right would indicate that the brain cavity within it was about as large as a man. -- Jayron  32  05:56, 12 January 2011 (UTC)


 * (ec) The sperm whale, according to its article. Largest body part says shrews have the largest brain-to-body mass ratio though. (Of course, the way you have it capitalized, it could be Eric Burdon.) Clarityfiend (talk) 05:58, 12 January 2011 (UTC)
 * Or the Sperm whale... Once I was out strolling when I laid myself to rest in a big field of tall grass... Sorry, had an Eric Burdon moment there. Anyhoo, yeah, it looks like the Sperm Whale's brain is bigger than the blue.  -- Jayron  32  06:03, 12 January 2011 (UTC)


 * If you want brain size in terms of number of neurons then List of animals by number of neurons might help you. Zain Ebrahim (talk) 11:04, 12 January 2011 (UTC)


 * Keep in mind that bigger doesn't mean best in this respect. For a more useful heuristic with regards to processing power, see encephalization quotient. --Mr.98 (talk) 15:48, 12 January 2011 (UTC)

Synthetic elastomeric polymer
whats Synthetic elastomeric polymer in caulk — Preceding unsigned comment added by Tommy35750 (talk • contribs) 05:56, 12 January 2011 (UTC)
 * The article elastomer has some examples of such substances. Different types of caulk will have different ingredients; is this silicone caulk, acrylic caulk, and what specific brand and type of caulk is it?  -- Jayron  32  05:59, 12 January 2011 (UTC)

viral inactivation in hpv blood
describe the neat skecth of viral inactivation in hv blood?with following flow chart? describe the neat skecth of viral inactivation in hv blood?with following flow chart? —Preceding unsigned comment added by 202.67.226.236 (talk) 06:15, 12 January 2011 (UTC) -- Jayron  32  06:20, 12 January 2011 (UTC)

Energy efficiency: bicycle vs. diesel motor
Which one is more efficient: a bicycle or a small modern diesel motor? Normally, beasts of burden are pretty inefficient, and humans are a beast of burden in this case, and diesel motor tend to be very efficient (and their performance is improving). So, if I mind about the environment, what should I choose? Quest09 (talk) 10:25, 12 January 2011 (UTC)
 * That depends on what you want to do, of course. For moving around an overfed person, using a bicycle is certainly more efficient, as you use energy that would otherwise just "improve" your waistline. If you go with a small car, you will almost certainly carry around 90% dead weight. If you look at it purely from a thermodynamic point of view (does a human or an engine produce more power per chemical energy input), the Diesel engine will win (it operates at a much higher temperature and hence better thermodynamic efficiency). --Stephan Schulz (talk) 10:46, 12 January 2011 (UTC)
 * As far as I'm aware if you discount basal metabolism and just count the extra work you can produce by eating a baked potato your body is about 40% efficient. This is bit better than a diesel car though the diesel engines in a ship can do better at over 50%. This is the major reason exercise is so ineffective at burning off fat and reducing weight, though of course it is much better because it makes people fit. Dmcq (talk) 14:50, 12 January 2011 (UTC)
 * Let's make things clear. Ther is absolutely no doubt that driving a bicycle is better for the environment than driving a diesel powered vehicle. Schulz makes the mistake of forgetting that one cannot "turn a person off" while operating the diesel engine so, as Dmcq points out, the person's basal metabolism must be subtracted from the person's total metabolism before comparing the bicycle's efficiency with an engine's efficiency making the bicycle by far the most efficient method of transportation. Dauto (talk) 15:09, 12 January 2011 (UTC)
 * It also depends on how you measure efficiency. Bicycles are devices to transport a person from one place to another. However, most devices to transport a person from one point to another with small modern diesel motors are cars. So if you're looking at the efficiency of transporting a person from point A to point B, the bicycle tends to be more efficient, because it's only transporting the person + 50 kg of bicycle, versus the diesel motor, which is transporting person + 1000+ kg of car. If, on the other hand, you're looking at the efficiency of transporting two adults and a table and chairs, the efficiency considerations can change. You need to know what you're really after when you ask about "efficiency". -- 174.21.250.227 (talk) 16:59, 12 January 2011 (UTC)
 * I won't trade your bicycle for my bicycle (and mine is already more robust than lightweight at 18 kg or so...). --Stephan Schulz (talk) 19:30, 12 January 2011 (UTC)
 * I don't know how efficient a plane is but it might be more efficient than a bicycle because it goes so fast. You have to count the cost of the basal metabolism for all that extra time travelling there on a bicycle. Dmcq (talk) 19:02, 12 January 2011 (UTC)

Is the question about thermodynamic efficiency or the more vague "energy efficiency" in the context of environmental conservationism? "Efficiency" means many different things. I think Quest09 is seeking one of these "embodied energy" analyses on the bicycle and the diesel motor. However, those analyses suffer notoriously from poor definition of boundaries and edge cases. Nimur (talk) 19:41, 12 January 2011 (UTC)
 * Diesel engines are almost unheard of in aircraft. Googlemeister (talk) 20:03, 12 January 2011 (UTC)
 * But seemingly not because of issues surrounding efficiency. Vespine (talk) 22:15, 12 January 2011 (UTC)

To bicycle 20 miles takes about 1000 extra calories. This is about 2lb of potatoes, which costs about $1.25. A small car can do maybe 30 miles per gallon? And a gallon costs $3, so it costs $2 to go 20 miles. Ergo the bicycle is more efficient if you eat potatoes. On the other hand you need two Big Macs to get 1000 calories, and they cost $3.57 each, so $7 for two. So if you eat Big Macs, it's more efficient to drive than to bicycle.

BTW, I am using cost as a proxy for energy usage because it correlates extremely well. You can't just look at the energy content of a gallon of gas vs a potato and ignore the energy used in growing, and harvesting the potato, but the cost includes those. Ariel. (talk) 22:54, 12 January 2011 (UTC)


 * Yes, but let's not overlook the cost of car insurance, the maintenance cost of a car vs a bike, and the extreme difference in up-front cost of a car vs a bike.    Cars are more about comfort, ease, range, and convenience -- on a minimal budget they are not so great. Vranak (talk) 15:08, 13 January 2011 (UTC)


 * That would be if you're cycling fast. If you do it a bit more leisurely one Big Mac would take you thirty miles. Dmcq (talk) 23:40, 12 January 2011 (UTC)

Four bar mechanism
is it correct ?? A four bar mechanism will have rocker inversion when which one of the following condition is satisfied. l + s > p + q —Preceding unsigned comment added by 59.93.131.117 (talk) 12:39, 12 January 2011 (UTC)
 * Have you taken a look at Four-bar linkage? //83.253.250.186 (talk) 13:07, 12 January 2011 (UTC)

CRO
Hi I am having a repaired Color TV of 21" can I convert that TV CRT into CRO? that will be help full for me because I am Electrical student. — Preceding unsigned comment added by Kanniyappan (talk • contribs) 13:38, 12 January 2011 (UTC)


 * For readers who are not familiar with the acronym, in this context a CRO is a cathode ray oscilloscope. TenOfAllTrades(talk) 14:24, 12 January 2011 (UTC)


 * Googling "converting tv into oscilloscope" throws up a few results. Certainly some people have done this, and you could have a look.  This result has lots of links.  But beware this warning from one of the pages: "Warning!!! Please note!!! There are high voltages inside tv sets! Use extreme caution! My advice is, never reach into the unit while it is plugged in unless you are real sure of what you are doing". --Colapeninsula (talk) 17:36, 12 January 2011 (UTC)
 * Old ads in electronics magazines told how you could convert a tv into a big screen oscilloscope. One problem is that you do not have available a wide range of sweep frequencies, unless you save only the tube and build all new electronics. It was easier to convert an oscilloscope into a video monitor. Oscilloscopes had electrostatic deflection of the vertical and horizontal trace, while TVs used magnetic coils, much less workable for widely varying horizontal weep frequencies and for high frequency sweep. See . I believe there are kits to get a computer to work as an oscilloscope as well. Edison (talk) 20:55, 12 January 2011 (UTC)

Pancreatic cancer image


What's pictured in this image: is it the pancreas itself, or something else? The image description isn't in English, and its caption at Pancreatic cancer ("Axial CT image with i.v. contrast. Macrocystic adenocarcinoma of the pancreatic head.") isn't simple enough for me to understand. Nyttend (talk) 15:04, 12 January 2011 (UTC)
 * It's a slice of the torso from a CAT scan. The lower-center white structure is a vertebra. The thing just to the right of it might be the heart. The little white streaks are slices of ribs. I'm not sure which thing the pancreas is. --Sean 15:31, 12 January 2011 (UTC)


 * I suspect the thing in the crosshairs (middle top left) is the pancreas and the cancer. There shouldn't be a heart in that picture — it's too low (note that you can see the formation of the buttocks/lower back). I think what you're labeling as the heart is probably a kidney? The big thing on the left should be the liver. Compare with the Gray's Anatomy photo I've added. The LR axis is flipped. An anatomist I am not, though. --Mr.98 (talk) 16:03, 12 January 2011 (UTC)
 * I think one of those images is viewed looking up (if the subject was standing, and the other is looking down. Googlemeister (talk) 19:14, 12 January 2011 (UTC)
 * Another way to think of it is that the CT is taken with the person lying down, and you are looking at a slice as though you are standing at their feet, which is the standard convention for radiographs like CT and MRI. The older Gray's Anatomy pic is indeed viewed from "above". Mr.98 is correct that the crosshairs are pointing at a mass (likely pancreatic cancer although you often need a biopsy to know the tissue of origin for certain). IANAR (I am not a radiologist) but I'm pretty sure that the long light-grayish structure that wiggles horizontally and diagonally through the middle of the CT scan is the rest of the body and tail of the pancreas. --- Medical geneticist (talk) 19:35, 12 January 2011 (UTC)

Heart was a good guess for the pepper-shaped thing, but as Mr. 98 stated, the scan is at a moderate level of the abdomen (there are only ribs in the back and not in the front, and so nothing from the thorax above the xiphoid process should show. The pepper-shaped thing looks like the large intestine.  DRosenbach  ( Talk 10:21, 14 January 2011 (UTC)


 * Good to hear, for a minute there, I thought my liver was on the wrong side. Googlemeister (talk) 16:13, 13 January 2011 (UTC)
 * Looks like it's the left kidney after all: . I don't think the colon sits that far back. I didn't understand it being a kidney since there's only one, but it does look like the left one sits significantly higher than the right:, . We need more labeled CT scans on Wikipedia. --Sean 17:13, 14 January 2011 (UTC)

Earnshaw's theorm: magnetic levitation
Ello, I want to challenge something about above:

Is it not possible to levitate say for instance a cone-shaped object inside another cone when permanent magnets are stuck to the inside of one and outside of the other cone in a polar array formation (all magnets repelling one another), thus producing concentric symmetry? Surely this is dynamic equilibrium in practice?

Please tell me if I'm wrong and why... —Preceding unsigned comment added by 209.203.29.62 (talk) 15:34, 12 January 2011 (UTC)


 * I think the answer lies in the stability of the levitating configuration. See Magnetic_levitation. Earnshaw's theorem only precludes stable levitation. In the system you describe, the upper cone may indeed levitate for a short period of time, but it will not return to the levitating state after small perturbations. SemanticMantis (talk) 15:58, 12 January 2011 (UTC)


 * Think about the magnetic field lines from just the outer cone (let's say the north poles are facing inward): they emerge from the inner surface, but they have to reach the outer surface somehow. If you have just a few magnets, the field will escape through the gaps; the gaps therefore appear to be south poles (since the field vanishes into the surface there, just like at a south pole) and the inner cone will spin/tip and stick its magnets into those gaps.  If you have a perfectly conical field, it must escape out the top of your outer cone, and you will find that the inner cone can't be inserted at all because the whole opening of the cone is a gigantic north pole.  --Tardis (talk) 16:29, 12 January 2011 (UTC)


 * In the latter case, getting the inner cone into the outer one is just a matter of applying enough force -- say, you could tie it down with weights. However, if the field point inwards everythere on the outer cone, the field must be stronger in the center of the cone than along the walls. Therefore magnets on the inner cone will be attracted to the outer wall, creating instability. (We could reverse the magnets on the inner cone, and then it would be horizontally stable, but we'd also reverse the levitating force that kept it from falling in the first place).
 * Beware that the idea of magnets "repelling one another" is simplified and inaccurate. A magnet that is oriented against the grain of the field does not really care about where the magnets that generates the field located; it just tries to go in the direction where the field is weaker. If that is closer to the sources of the field (as can happen inside a concave surface covered with magnets) then so be it. –Henning Makholm (talk) 19:37, 12 January 2011 (UTC)

Winter
Why is it coldest in late January, even though the days are getting longer? 74.15.137.130 (talk) 16:03, 12 January 2011 (UTC)
 * Your IP geolocates to Montreal. Is this the region you want answers about? SemanticMantis (talk) 16:16, 12 January 2011 (UTC)


 * The surface is always losing heat into space at a rate that depends on its temperature; for any given solar input there will be some temperature where there's a balance, but it isn't reached immediately because there's so much planet to heat/cool. That equilibrium temperature is a function of the solar input (the season) along with surface conditions, but let's ignore those so it's least at the December solstice.  Therefore the "target temperature" to which the hemisphere tends is lowest then, but it's still cooling down towards that temperature from the autumn temperatures.

In late January, as it happens, the target temperature (going up) crosses the actual temperature (still dropping) and so the actual temperature doesn't drop any more and begins rising to chase the target. It's exactly the same effect that puts the lowest temperature in a day some time after dawn. --Tardis (talk) 16:20, 12 January 2011 (UTC)


 * The simplest answer is that the Earth takes a long time to heat up or cool down, being so huge. Just like a pot doesn't intantly cool down to room temperature the second you take it off of the stove, the Earth does not instantly cool down or heat up with the solstices.  While, in the northern hemisphere, the day of shortest insolation is in December, it takes about a month for the Earth to stop cooling off and start heating up again in response to the longer January days.  -- Jayron  32  17:56, 12 January 2011 (UTC)


 * Thermal inertia is one of many complicated inputs into a model of climate. You might want to read about global climate models to see how scientists attempt to bring observed fact (such as the temperature profile for a region) in line with theoretical expectations (such as a thermodynamic analysis of input and output energies).  Nimur (talk) 19:48, 12 January 2011 (UTC)


 * Jayron's example above is misleading, because a pot does instantly start cooling down to room temperature the second you take it off the stove. The difference with the Earth is that near the solstice the length of the day is only changing very slowly.


 * So instead of imagining putting a pot onto the stove or taking it off again, with the burner at a constant setting, imagine a pot (of some dry material that won't boil) left constantly on the stove while you s....l....o....w....l....y turn the burner from 1 up to 10 and then back down to 1 -- moving it the most slowly when it is near the 1 or near the 10. Suppose that if the burner was left at 1 then the temperature in the pot would settle at 60°C; at 2, 70°C; at 3, 80°C; and so on up to 150°C at a setting of 10.


 * Will it ever reach 150°? No, because you only have it set at 10 briefly.  Perhaps it has warmed as far as 125° when you reach a setting of 10.  When you lower it to 9, it is still heating because it has not yet reached 140°, the temperature that that setting would produce.  Perhaps it reaches 130° by the time you turn it down to 8, and after that it begins cooling.  Same thing at the other end of the cycle: when the setting reaches 1, the pot might be at 85°, and it will continue cooling until it reaches 80° at the point when the setting reaches 3 on the way up, after which it will start rising.


 * See? --Anonymous, 07:22 UTC, January 13, 2011.

Okay thanks. Oh, and it is now my New Year's resolution to use geolocate seriously in a conversation. 74.15.137.130 (talk) 22:40, 12 January 2011 (UTC)
 * It's a perfectly cromulent word, meaning to perform geolocation... though it seems location more specific than hemisphere is largely irrelevant for the answers given so far. SemanticMantis (talk) 16:47, 14 January 2011 (UTC)


 * I think the simplest explanation is this: A region gains heat when the amount absorbed from the Sun exceeds that is lost to space. Solstices are when the Sun rays reaching the surface start to increase or decrease, but past the winter solstice a region in the Northern hemisphere is still losing more heat than it absorbs. Only when the days get long enough does that change. When it does, the region will warm up. Imagine Reason (talk) 01:42, 15 January 2011 (UTC)


 * High pressure systems typically dominate over Quebec around this time of the winter, and resulting cold waves directly from the polar vortex can occur. ~ A H  1 (TCU) 03:12, 18 January 2011 (UTC)

Hypnosis
Real or not? I say it is. Accdude92 (talk) 17:00, 12 January 2011 (UTC)


 * Have you read our articles on hypnosis and related topics? Also, the question of "real or not" is heavily dependent on what sort of hypnosis you're talking about and what you mean by "real".  For the former, medical uses of hypnosis are vastly different from stage hypnosis.  For the latter, stage hypnosis acts undoubtedly occur (stage hypnosis is "real") but may well not be based on traditional hypnotism (stage hypnosis is not "real"). &mdash; Lomn 17:13, 12 January 2011 (UTC)


 * Are you asking whether the recovered memories are real? There is also the risk of creating false memories due to suggestability, but also read psychological repression. ~ A H  1 (TCU) 03:10, 18 January 2011 (UTC)

Woibbly fridge
My gf says a wobbly fridge doesnt work as efficiently as a stable on. Is she correct?--92.28.46.3 (talk) 18:00, 12 January 2011 (UTC)
 * Depends on which part is wobbly. If the door won't stay shut, it is definitly less efficient.  Furthermore, its not hard to fix.  Jam some folded-up paper under one of the corners.  It'll stop wobbling. -- Jayron  32  18:23, 12 January 2011 (UTC)


 * Is her complaint that the compressor needs to be perfectly aligned horizontally for maximum efficiency, or does she suspect inefficiency for some other reason? Comet Tuttle (talk) 18:52, 12 January 2011 (UTC)
 * Might she be making a thermodynamic argument, that the wobble represents energy lost to mechanical vibration, and eventually dissipated acoustically and as heat? Your girlfriend might be interested to read about how refrigerators work, and refrigeration thermodynamics.  Actually, everybody should read about refrigerator thermodynamics.  It would be a good thing for the world to know more about thermodynamic efficiency.  As we know from the three laws of thermodynamics (which I have interpreted for this specific situation):
 * The refrigerator is going to use energy; but even if it doesn't, the same energy will just get used up somewhere else. So "efficiency" only really has context from the anthropocentric viewpoint that it's important to keep food cold.
 * Even if the energy gets wasted in wobbling a motor, it'd just get wasted as heat anyway. That's how refrigerators work.
 * After a long enough time, that waste heat is going to be uniformly spread throughout the entire universe, so in the long run it's actually more efficient to just wait for the food to get cold by itself.
 * Nimur (talk) 19:57, 12 January 2011 (UTC)
 * I think the OP is interested in his electricity bill, not in the end of the universe. --Lgriot (talk) 09:44, 13 January 2011 (UTC)
 * Intuitively, from just a rotational dynamics consideration, I'm convinced that she is correct, but I can't find any published research to confirm this. I also suspect that the effect will be small compared with other inefficiencies in the system unless the wobble is large.    D b f i r s   11:40, 13 January 2011 (UTC)
 * I'm surprised that nobody has pointed out that it takes energy to make it wobble, and the energy comes from electricity, which you have to pay for. So a wobbling fridge is bound to be less efficient than exactly the same fridge which does not wobble. 92.15.24.16 (talk) 13:06, 15 January 2011 (UTC)

Electroweak interaction
Why was it easier to unify the weak nuclear force with electromagnetism rather than the strong nuclear force? Aren't the two nuclear forces more closely related to one another? --J4\/4 &lt;talk&gt; 18:36, 12 January 2011 (UTC)


 * No, evidently not. Their only similarity (compared to electromagnetism) is that they have limited range, and therefore both show up only in nuclear phenomena. But the short range arises, as far as I understand, for entirely different reasons. –Henning Makholm (talk) 19:09, 12 January 2011 (UTC)
 * Worth pointing out that electroweak theory really isn't a unifyed theory anyways in the sense that within the electroweak theory there are still to completely independent interactions (that is non-unified interactions) refered to as weak isospin and weak hypercharge (not to be confused with the flavor isospin and flavor hypercharge which are not gauge interactions.)Dauto (talk) 05:09, 13 January 2011 (UTC)

Flower identification/information needed
Hello folks, can anyone tell me what to make of this flower blossom? To give a bit of background, this is a blossom on an anthurium plant belonging to my gran. The plant has had normal blossoms (the kind you'd expect on this sort of flower) for at least five years; it has a couple right now, too, but recently developed this blossom (which almost looks double-flowered). I've never seen anything like it before, and neither did the employees at various flower stores and the local botanical garden.

If anyone can shed some light on this, I'd be very grateful. Thanks! :) -- Schneelocke (talk) 20:50, 12 January 2011 (UTC)


 * Looks like an aberrant flower form; this may happen sometimes. I do not know if this is caused by injury, age, genetic makeup of this particular hybrid, or a combination of those factors. Googling for "anthurium double spathe" returns quite a few hits. Also, I've seen aberrant orchid flowers on quite a few occasions with an extra labellum or two, usually where the petals should have been, co-occurring with normal flowers. This may be a result of selective (in)breeding. There's no reason why this couldn't happen to anthurium as well. Hope this helps. --Dr Dima (talk) 21:39, 12 January 2011 (UTC)
 * Yes there are many factors that could cause such a thing. I doubt selective inbreeding is the main cause, because all other blooms on the plant have been 'normal'. On the genetic front, it could be mutation in the progenitor stem cells from which the bloom developed. Also certain plant pathogen viruses can manipulate host DNA. These and other epigenetic processes seem likely culprits to me. You can propagate the cluster holding the aberrant bloom via stem cutting as described here . If that plant continues to produce the same type of bloom, that would be evidence toward mutation in the stem cells. Any other ideas? SemanticMantis (talk) 15:13, 13 January 2011 (UTC)

dogs and cats
Does science recognize any creature as being a common ancestor of both dogs and cats? Bus stop (talk) 20:59, 12 January 2011 (UTC)


 * Do you mean a existing species? Then no.  But, there are certainly many fossils that are plausibly ancestors of both.  See Carnivora, Miacid, Synapsid, etc.  Dragons flight (talk) 21:14, 12 January 2011 (UTC)


 * Looks like it would have been some sort of Miacoidea, but I cannot find anything more specific. There is still some debate about phylogeny and evolution of carnivora, in particular regarding the Caniformia/Feliformia split, but see Cat-gap for some current hypotheses. SemanticMantis (talk) 21:30, 12 January 2011 (UTC)


 * (Edit Conflict) Yes. Cats (Family Felidae) and dogs (Family Canidae), along with various other Families, are both members of the Order Carnivora, all of whose member families are by definition descended from a single progenitor species. This would have been a member of the older (and now entirely extinct) miacid Family Miacidae, probably a member of the Genus Miacis, and probably lived around 42 50 million years ago.


 * However, although we know of at least one species of Genus Miacis, Miacis cognitus, we cannot be sure if this particular species was the Most Recent Common Ancestor of the carnivores, or whether it was a (probably similar) sister species, of which fossils may not have yet been (and may never be) found - only a small fraction of all extinct species, with or without descendents, have been found as fossils, as fossilisation is a very rare event. In short, we are certain that there was such a common ancestor species of all Carnivora, and know roughly when it lived and what it it was like, but can't point to a particular fossil and say "This was one of them."


 * Within the Order Carnivora, the lines that gave rise to the Felidae and Canidae (and which also included what subsequently became civets and mongooses, and bears and seals, respectively) probably diverged only a few million years after the Order's origin, but the details of this are not yet well understood. Considering the major differences between some of their respective closer relatives, it's interesting that the skeletons of cats and dogs themselves have remained so similar. To summarise, although cats and dogs as we now recognise them did not spring directly from a common ancestor, the cat-like and dog-like Sub-Orders, Feliformia and Caniformia, to which they belong did do so.


 * Surprisingly, the closest surviving relatives of the Carnivora are (probably) the Pangolins. For the beginnings of answers to many similar questions, may I recommend Richard Dawkin's book The Ancestor's Tale. 87.81.230.195 (talk) 21:38, 12 January 2011 (UTC)


 * Yes, most recent common ancestor would probably be what I was inquiring about. Thank you for those explanations. I guess it would be hard to point to some extinct creature that was both the origin of biological family Felidae and the biological family Canidae. Bus stop (talk) 00:00, 13 January 2011 (UTC)