Wikipedia:Reference desk/Archives/Science/2009 January 25

= January 25 =

Burying charcoal to mitigate global warming
James Lovelock recommends burying charcoal in a non-biodegradable fashion. What are the advantages and disadvantages of this form of mitigation?

''Note: I originally asked this question at Talk:Mitigation_of_global_warming before it occurred to me that this reference desk might be a better place to ask. Would you please answer at that talk page instead of here?'' 69.228.235.107 (talk) 02:55, 25 January 2009 (UTC)


 * The talk page of articles isn't really the place to ask such questions as they are solely for discussions about improving the article. Technically your question could be removed although I'm not suggesting anyone does so. Since no one has answered there I would suggest you simply direct people here. Nil Einne (talk) 06:17, 25 January 2009 (UTC)


 * The reason I asked was because I had hoped to improve the article. 69.228.235.107 (talk) 07:42, 25 January 2009 (UTC)


 * I understand that, but most of what's being discussed here has nothing to do with improving the article, as with most RD questions particularly those of this sort which are likely to result in a far amount of discussion which isn't directly sourced. It possible you may eventually get something here which could be added to the article but that's not really the purpose of article talk pages. In talk pages like that, no one tends to mind but in extremely active ones any sort of OT talk such as a question like this will often be deleted or archived or at least you may get people telling you to ask it somewhere else. So it's a good idea to get into the habit of asking questions like that here, your far more likely (in general) to get an answer and it's also easier for someone to find the discussion in future Nil Einne (talk) 08:18, 25 January 2009 (UTC)


 * He talks about plowing it into farmer's fields, but then plant roots would get at the carbon, pull it into the plant, and make it part of the carbon cycle again. Carbon sequestering requires putting the carbon somewhere that life can't get to it. StuRat (talk) 06:16, 25 January 2009 (UTC)


 * Note that the OP (and the linked article) said non-biodegradable charcoal. I'm not aware there is any form of charcoal that isn't relatively biodegradable although I guess you could make some sort of plastic with it. There's also the question of whether having all this non-degradable material is going to eventually prevent plants from growing when you end up with too much of it. Nil Einne (talk) 06:21, 25 January 2009 (UTC)


 * Why charcoal? To make charcoal, you take a lump of wood - and heat it to drive out the water...why bother?  The production of that heat uses energy - and that almost certainly produces CO2 which diminishes or even eliminates the benefits of burying the charcoal.  Why not just bury the wood?   The actual business of burying in farmland seems difficult too - dumping it in old coalmines or worked out open-cast mine pits (and then covering with dirt) would be better. SteveBaker (talk) 06:25, 25 January 2009 (UTC)


 * Why charcoal? Because you just want to make sure that the carbon stored in the plant growth doesn't get released as carbon dioxide. If you bury wood, it quickly gets broken down and the carbon is released as carbon dioxide. If you can convert it to nonbiodegradable charcoal (and I don't know how feasible the methods given really are; I agree with the potential effect on farmland) the carbon won't get released as carbon dioxide unless someone burns it. Sure, a little carbon dioxide is produced in making the charcoal, but not nearly as much as would have been produced if the whole thing was broken down as happens when you bury wood or plough your stubble back into a field. 79.66.105.133 (talk) 12:34, 25 January 2009 (UTC)

Here is an idea. Why don't we just grow trees, cut them down and turn them into furniture. Won't this be just another form of carbon capturing technology? We will make a law that says it is illegal to burn furnitures. 122.107.203.230 (talk) 06:55, 25 January 2009 (UTC)


 * @StuRat plant roots don't usually process/transport carbon in plants AFAIK. They draw CO2 from the air for photosynthesis and minerals and water from the ground.  But there are a lot of chemical processes going on in soil.  As soon as the carbon has reacted and been bound into something that a fungus can use it's back in circulation.  These guys also seem to find it palatable .  Plowing under the charcoal doesn't sound like a good idea .  The article doesn't concern wood specifically grown for carbon sequestering, but farm waste like straw.  If you'd compare firing your hearth with straw to using charcoal you might come out ahead, but most of the biofuel from farm waste processes have so far proved to be uneconomical or coming with a negative energy balance.  That's one reason why we now make ethanol from sugar rather than straw. (Also see wood gas.)  Transporting the charcoal made from straw to a coalmine and sinking it into the pit would also consume energy.  Digging up coal and then sinking charcoal in it's place sounds a bit odd anyway.  The BTUs you get out of charcoal don't differ that much from what you get from coal (Can't link it, but it's ard. 9,000 BTU for charcoal and 6,000 - 14,000 for coal. The numbers for charcoal from straw would come out somewhat different, though.)  That method would also be chucking a lot of nutrients plants need into the hole. You'd either have to separate those out or wait till they concentrated at the bottom and dig them up again after a considerable period. I guess they stumbled over that argument and then refined their original idea to "plowing it under".  You'd have to move it to the processing plant and then move it back and spread it onto the field, that would consume energy.  If you converted it into charcoal on the field you'd lose the "biofuel" advantage they touted and I guess then their calculations would not come out ahead. Reminds me of the saying, "It's the technology of the future - and always will be." 76.97.245.5 (talk) 10:40, 25 January 2009 (UTC)

Surely this entire discussion is based on a misunderstanding. It isn't Carbon we want to sequester, but CO2. Surely charcoal is essentially carbon. Planting trees is good because it takes CO2 and breathes out O2 whilst making the C into "tree". -- SGBailey (talk) 11:34, 25 January 2009 (UTC)


 * I believe that the idea is that excess carbon in the biosphere will readily be combined with oxygen from the air to form carbon dioxide. StuRat (talk) 14:55, 25 January 2009 (UTC)


 * Thus far it (mostly) works. The problem arises when you then burn or decompose the tree. That creates greenhouse gases (CO2).  Which is why the guy in the linked article came up with his idea.  Charcoal can be created in an anaerobic process (see Pyrolysis).  That way less CO2 would be released into the atmosphere.  The question is whether the big picture will come out as producing CO2 as a consequence of any component necessary to get from tree (or straw) to charcoal in the ground and whether the charcoal stays in the ground or is used up to make CO2 down the line.  There are many examples of seemingly good ideas that turned out to be huge mistakes once all the consequences became obvious. 76.97.245.5 (talk) 13:11, 25 January 2009 (UTC)


 * Also, won't burning massive amounts of organic material in a low oxygen environment to produce charcoal also produce carbon monoxide ? StuRat (talk) 15:02, 25 January 2009 (UTC)

It looks like Biochar is a fairly well-developed article on the topic. 69.228.235.107 (talk) 16:42, 25 January 2009 (UTC)

Rope bridges over big gaps
[Posting here because it's the closest to engineering] Before modern technology (i.e. helicopters), how were big rope bridges built over gorges? I'm guessing that a small bridge, maybe even something like the Carrick-a-Rede of 20 metres, could be begun by someone strong throwing a rope all the way across the gap, but Inca rope bridge discusses one of 67 metres. I could understand if these were low bridges over rivers, but seeing that these connect cliffs dozens of metres high, I'm assuming that it's not possible simply to carry the rope over. Nyttend (talk) 04:28, 25 January 2009 (UTC)
 * You do need someone at each end of where your bridge will be, and you do need to get the rope across - the trick is, you don't try to throw a big heavy rope. You throw a thin, light rope, and use that to haul thicker ones across. Tying a monkey's fist, or a stone, in the end of the light rope makes it easier to throw accurately, and by swinging it around before releasing it will go further. If the chasm is too wide to throw even a light rope across, then you throw it across at the bottom and then climb the sides, paying out as you go. DuncanHill (talk) 04:57, 25 January 2009 (UTC)
 * If you can't climb the sides of the gorge at the point you want the bridge, then climb down where you can, and walk along to a point below the bridge site. Your colleagues at the top of the gorge lower a line to you (the same being done on the other side), and you attach this line to your heaving line. The heaving line is then pulled up to the top of the gorge. DuncanHill (talk) 05:01, 25 January 2009 (UTC)
 * It would be a lot easier to explain with a) some rope, b) a suitable gorge, and c) a plentiful supply of Scouts to run around carrying things. DuncanHill (talk) 05:16, 25 January 2009 (UTC)
 * "Plentiful" gave me another clue: If you have at least three people, you can have one on each side throw down a line to a third one at the bottom. The third person just ties the two lines together, and voilà! &mdash; Sebastian 05:23, 25 January 2009 (UTC)
 * Now that's good! I must remember that :) DuncanHill (talk) 05:28, 25 January 2009 (UTC)


 * The idea of pulling a very fine thread across - and then using that to pull a thicker rope - and that up to the full-sized rope makes sense. But if a fine thread is all you have to get across there then a bow and arrow would get it over there.  Perhaps even a trained bird of prey could carry enough fine thread across the gap.  Modern archers using 'traditional' bows shoot at targets at 50 yards (and 90 yards is common with modern bows) - it's clear that the best archer the bridge constructors could find could make an arrow go 67 meters...given that accuracy and penetration of the target are irrelevent.  However, the Inca's didn't use bows - they used slings...but (amazingly) our sling (weapon) article says that a slinger could fling a rock 600 meters(!) - ten times more than is needed here!  So IMHO, it's overwhelmingly likely that this is what they would do. SteveBaker (talk) 06:35, 25 January 2009 (UTC)
 * The slings and arrows of outrageous bridge-building... DuncanHill (talk) 16:55, 25 January 2009 (UTC)

A kite with a following wind could carry a cord for miles...... 196.2.124.248 (talk) 07:40, 25 January 2009 (UTC)


 * In fact, a kite is exactly what they used in 1848 to begin the construction of the first bridge over the gorge at Niagara Falls. A prize was offered to the first boy to perform the task.  --Anonymous, 04:53 UTC, January 26, 2009.

That reminds me when I was wondering how spiders do it. I know they can drift in the air, but I've seen a web anchored at two branches from different trees, with the upper anchoring points about 8 m apart and about at the same height. Since the spider's body was about 1 cm long, and it was in a dense forest where you wouldn't expect strong winds, I can hardly imagine that the spider drifted horizontally for 8 m. &mdash; Sebastian 05:19, 25 January 2009 (UTC)


 * @Sebastian There are several ways that spiders get that gap bridged. As described in Spider web some dangle a sticky thread to float in the winds till it gets caught somewhere. Sometimes they also use rappelling, swinging themselves to and fro till they get to a good spot. They lengthen or shorten the thread they are hanging on as needed.  Then there's Ballooning (spider) although that's more commonly used to get away from close relatives.    (Know thy enemy.  Arachnophobia is less productive than informed avoidance.:-)  Did Incas use Blowguns?  Our article doesn't say, but it isn't a new weapon and is widely used throughout the Americas.  I'm not sure you could tie a thread to a dart, though.  The slingshot method looks like the most likely scenario.  76.97.245.5 (talk) 08:51, 25 January 2009 (UTC)


 * You're right, they just use the threads alone, so the weight of the spider does not play a role. Still, it is amazing that they manage to bridge 8 m that way, even in a calm forest! &mdash; Sebastian 23:12, 25 January 2009 (UTC)


 * It seems amazing to us chunky humans - but remember that air resistance is proportional to cross-section which is proportional to the square of the size of the animal - but weight is proportional to the cube of the size of the animal - so at the scale of a spider, wind is a force that's VASTLY more powerful than at our scale of experience. A 1cm spider experiences 200 times the amount of wind force (pound-for-pound) than a 2m human does.  So we might consider 40cm to be bridgeable with a human-scale parachute in a modest breeze...8m is a snap for a spider. SteveBaker (talk) 02:03, 26 January 2009 (UTC)

Circuit schematics: are these good?
I've designed the circuits and, based on  and , respectively, and I was wondering if someone could audit the designs for me. I'm planning to build them both and I want to make everything is correct before I order my parts and/or start soldering. I don't things to blow up or to have to spend a lot of money on more parts and/or shipping.

So would these circuits work, theoretically? If there's anything even remotely wrong, please let me know so I can fix it before buying parts. -- Link (t&bull;c&bull;m) 10:22, 25 January 2009 (UTC)


 * I haven't looked at them but the usual thing to do is run them through a simulator, for instance a version of SPICE for analogue circuits, and see what happens. Dmcq (talk) 11:32, 25 January 2009 (UTC)


 * There are a number of diy electronic forums on the net which are probably a lot more suitable for this. On a quick look though you're not going to lose a lot of money so why not just go for it? You can always socket something expensive and it's unusual to destroy things if you get the power the right way round and ground yourself. Dmcq (talk) 11:57, 25 January 2009 (UTC)


 * Your first two links are PostScript files, which I can print, but can't view (there are PS viewers, but I don't have one). You might want to provide them in another format. StuRat (talk) 14:38, 25 January 2009 (UTC)

Death by toaster?
I have a habit of fishing bagels, muffins etc out of my toaster with a knife, without switching off the power. People are always telling me that this is dangerous because I risk getting a shock. I have always assumed that touching the elements would be no more dangerous that touching the elements on an electric grill or hob. Am I dicing with death everytime I have a crumpet? ToastShock (talk) 10:38, 25 January 2009 (UTC)


 * It depends upon what country you are in. In the UK, the two ends of the toaster element are neutral and live. Iff your socket and toaster are wired correctly then when it has "popped up", one end of the element will be disconnected from the live supply. If the wiring is wrong, it could be the neutral that is disconnected, in which case you stand a chance of connecting to live. I suggest you use a wooden kebab skewer in future or better yet unplug the toaster. -- SGBailey (talk) 11:13, 25 January 2009 (UTC)


 * On my toaster (made in China for Philips, sold in Canada), when it has popped up, the element is disconnected from both sides of the plug: in other words, the switch is a double-pole one. I noticed this feature when looking at the wiring of a previous toaster and have just verified it for my present one by using an ohmmeter while it was unplugged.  But, of course, even if your toaster has this safety feature, you should not count on it!  --Anonymous, 05:16 UTC, January 26, 2009.


 * Yes, and it isn't even spectacular enough for the Darwin Awards Dmcq (talk) 11:45, 25 January 2009 (UTC)


 * Following EC: I'd definitely say you are tempting fate. There are safeguards like fuses, circuit breakers and improved Toaster designs that should take effect in case of an accident.  But you are basically relying on those working properly and you not accidentally switching the toaster on or creating a contact. I don't know your grill, but the heating element wires in a toaster are live when the toaster is on .  If you damage the insulation you may also create a short to the case and then get shocked when you touch it the next time you make toast.  There are a couple of people each year who win the "shouldn't have done that" lottery.

The saying goes: "Engineers try to make things fool-proof but fools always prove to be ingenious." Unplug the toaster and use a basting brush or rubber dough scraper if something got stuck. 76.97.245.5 (talk) 11:50, 25 January 2009 (UTC)


 * I'd change that last sentence to "or", as you don't need to take any other precautions besides unplugging the toaster, since they don't contain capacitors or batteries (which store electricity). So, once it's unplugged, it's perfectly safe.  Also note that if we are including everything that can possibly go wrong, then those toasters with metal housings can also be charged electrically, if a live wire is in contact with the exterior.  This could be true when the toaster is on, or off, or both.  This, in conjunction with you having wet hands and standing barefoot in a puddle of water connected to ground, and touching the outside of the toaster could cause you to become, well, toast. StuRat (talk) 14:32, 25 January 2009 (UTC)


 * I mentioned the soft implements because people have managed to create a short by poking a fork or knife into their toaster and then got zapped when they touched it later, or it started a fire. (Came up during a seminar on warning labels in user manuals, too lazy to look for a web reference.)76.97.245.5 (talk) 15:30, 25 January 2009 (UTC)


 *  --Kurt Shaped Box (talk) 14:38, 25 January 2009 (UTC)
 * You could always get a pair of toaster tongs. I haven't had a pair since I was a kid but basically it's a pair of tongs that are made of plastic and you stick them in to get your bread, bagel, etc out.  Since they aren't made of metal, they won't give you a shock.  Dismas |(talk) 16:50, 25 January 2009 (UTC)


 * Um...and who in the right mind would manufacture a knife without a non-metal handle?! ~ A H  1 (TCU) 17:51, 25 January 2009 (UTC)
 * All of our cutlery has metal handles.  for example makes steel-handled kitchen knives.  They're pretty common. SteveBaker (talk) 20:31, 25 January 2009 (UTC)
 * Your have any dinner-knives in your flatware set? Also, it's not necessarily the knife itself that conducts via its handle to the person, it could just be the blade that shorts to other metal parts (as others mentioned) such as an outer metal surface, which is why chassis grounding (the "third prong" on US plugs) is an important safety feature. I've always heard it as "build something idiot-proof, and the world will build a better idiot". DMacks (talk) 17:55, 25 January 2009 (UTC)

The stovetop or "hob" heating element does not generally have the energized wiring exposed. Calrod heating elements have resistance wire (nichrome) insulated by ceramics from the outer metal shell. Only if the insulation broke down and the outer shell were not grounded would it be energized. In a toaster, by contrast, the nichrome resistance wire is directly exposed to the toast, for faster and more efficient heating. If your fork or knife touches the heating element in a toaster, and you are touching the knife metal and something grounded, you are likely to be electrocuted. Unplugging before toast extraction seems like a fine idea. Edison (talk) 23:23, 25 January 2009 (UTC)


 * I was wondering when someone was going to point out the difference in the heating elements. (Fixed your confusing typo in the first sentence.)  --Anonymous, 04:57 UTC, January 26, 2009.


 * Re knives with plastic handles or other, I'd like to restate that it is inadvisable to use any implement with an increased danger of dislodging wires or damaging insulation inside a toaster, whether it is unplugged at the time or not. I lived in quite a few places where relying on the grounding of your home wiring system being up to code as DMacks suggested would have been folly.  Even in "3-prong" outlets I've seen way too many that weren't connected, weren't connected properly or had a grounding wire from the patch panel ending somewhere in a wall after s.o. had done some remodeling. (Arguably the most egregious one.)  In the US plugging in an adapter so you can plug in a 3 prong plug into an 2 wire outlet - without actually connecting the ground terminal - is an all too common practice.  There are those little circuit tester plugs with LEDs that will help you verify your wiring.  Using soft implements and thus reducing the risk of causing damage to the innards of your toaster seems like a hardship one can suffer. 76.97.245.5 (talk) 05:28, 26 January 2009 (UTC)

Choice of anticoagulant
Why is warfarin the anticoagulant of choice in the US and UK? What is its advantage comparing to heparin? What is its advantage comparing to acenocoumarol? --Mr.K. (talk) 12:27, 25 January 2009 (UTC)
 * I can't answer your question specifically, but a Google search reveals the advantages/disadvantages of both in different diseases such as venous thrombosis. Another two searches can show you the comparison between low-weight molecular heparin and warfarin against acenocoumarol. —Cyclonenim (talk · contribs · email) 12:41, 25 January 2009 (UTC)
 * Compared to heparin, the warfarin article states: "Warfarin is slower-acting than the common anticoagulant heparin, though it has a number of advantages. Heparin must be given by injection, whereas warfarin is available orally." -- Aeluwas (talk) 13:01, 25 January 2009 (UTC)
 * Is that a huge advantage? It looks like warfarin is just more convenient...Besides that is there any medical advantage?--Mr.K. (talk) 13:04, 25 January 2009 (UTC)
 * Of course it's a huge advantage! It's the difference between being able to walk around and carry out the daily activities of one's life, vs. lying in a hospital bed receiving intravenous fluids 24 hours a day! - Nunh-huh 13:46, 25 January 2009 (UTC)
 * It doesn´t say that it has to be intravenous. Heparin can be administered as subcutaneous injection. --Mr.K. (talk) 20:07, 25 January 2009 (UTC)
 * Subcutaneous heparin is sometimes used in bedridden or hospitalized patients as a means of preventing deep venous thrombosis or pulmonary embolism, but is not an effective means of fully anticoagulating someone - say in the setting of an artificial heart valve. In those settings - true anticoagulation, in which an actual change in blood parameters of coagulation can be measured - intravenous heparin is used because it has an immediate effect and is titratable to maintain an appropriate level of anticoagulation. After a few days, coumadin is started, because it - unlike heparin - has an oral dosage form which enables the patient to go home. Though they are both used for anti-coagulation, it's not like there's an actual "choice" between them: you use the one that the clinical situation dictates you use. - Nunh-huh 20:19, 25 January 2009 (UTC)
 * 'More convenient' often equates to significant medical advantage. Patient compliance with a treatment regimen is often better when the treatment is less painful.  Oral drug administration doesn't carry the same risk of infection associated with repeated (intravenuous or deep subcutaneous) injections.  There are social benefits associated with lower cost-of-treatment, reduced packaging, and the elimination of biohazardous sharps waste.  The patient can much more easily self-administer warfarin while working or travelling.  Huge advantages. TenOfAllTrades(talk) 17:21, 25 January 2009 (UTC)


 * Drug interaction and manufacturing defects  might sway the decision one way or another .  BTW. cinnamon contains varying amounts of coumarin.  OR 2 years ago I asked the FDA whether they monitored levels and they answered "cinnamon is considered safe and is not tested"  but coumarin as a food additive is prohibited! 76.97.245.5 (talk) 13:57, 25 January 2009 (UTC)
 * There are lots of natural food materials that are (un)regulated as food but that contain chemicals that are not allowable as additives. See Cyanide for example. DMacks (talk) 17:50, 25 January 2009 (UTC)

Regarding heparins vs. coumadin: Unfractionated iv heparin may be preferable in certain settings (ability to rapidly reverse anticoagulation being the primary one, some advantage in DVT's that extend on coumadin, etc.), but these are situations where patients should be in the hospital. In patients with cancer at high risk for deep venous thrombosis, low molecular weight heparin has been shown to be superior to coumadin in at least two prospective randomized control trials. Aside from these reasons, the convenience and other factors cited by others are the major ones. I'm not sure why other coumarins never made it to the forefront (cost? half life? developed later than coumadin?) -- Samir 08:21, 26 January 2009 (UTC)

help
While trying to get the tennis, my mother has managed to turn the normally colour digital TV through the set top box into black and white. Obviously she hasn't a clue how to undo this, and I have no idea how she did it, so how can this be undone? —Preceding unsigned comment added by 81.132.159.158 (talk) 15:00, 25 January 2009 (UTC)


 * Do you have a make and model ? There is likely a color setting which has been turned down to a very low level. StuRat (talk) 15:06, 25 January 2009 (UTC)


 * Turning the saturation setting down will turn a color image into a grey scale one. Check under the menu for image settings or the like. This seems more likely since it affects all the channels. I've also managed to lose color for certain stations when the receiving antenna was moved. (this was about 6 years ago on a homemade setup though.) I suppose you could try moving the set top box and making sure there is nothing sitting on it and checking to make sure the connectors are securely in place. I would check the color settings first. 152.16.15.23 (talk) 23:19, 25 January 2009 (UTC)


 * Check the cables between your set top box and the TV. Component cables carry brightness information on a separate cable from the color information. Also, S-video cables carry brightness information on a separate pin from the color information. If these kinds of cables are loose or damaged, this might cause the picture to become black and white. --Bavi H (talk) 04:44, 27 January 2009 (UTC)

communicating space tube
Following the "space tube" question above (Jan 24): Would the picture change if the tube ended in a U bend. (Provided such a tube could be constructed and wouldn't collapse due to the forces it was exposed to.) I was reminded of something, but had forgotten what it was called. I searched through 3 languages and I don't think we have a page. (Spanish and German do) We do have an image that says it's communicating vessels. (Should s.o. maybe do a page?) So would this be an effect to watch out for with that hypothetical space tube? 71.236.22.103 (talk) 16:35, 25 January 2009 (UTC)


 * Can you describe this tube a little more precisely? Where is the U bend and how big is it? Are you talking about a tube that has both ends in space, and just the bottom of the U in the atmosphere? Or something else? --Tango (talk) 17:10, 25 January 2009 (UTC)


 * The German article that image comes from is de:Kommunizierende Röhren which seems to be describing a tube linking two vessels which results in the liquid finding a common level in both vessels. It makes no difference, U-bend at the top, U-bend at the bottom, no atmosphere would leak out into space (other than what we are already losing by "evaporation").  The bottom line is that it requires energy to remove anything from earth and that energy has to come from somewhere.  A passive tube, no matter how cleverly you bend it, can never provide any energy.  This kind of thing is like perpetual motion machines, it can't be done because of a fundamental law of nature, but for each one you disprove, someone comes along with a more complex one that apparently allows it to work, but always there is a subtle, or sometimes not so subtle, flaw in the argument. And always it will come down to that same law of nature, conservation of energy.  Sp in ni  ng  Spark  00:33, 26 January 2009 (UTC)
 * Yep - after enough years looking at silly ideas like this - you eventually learn that it's a waste of time to track down the root failure of the idea. The laws of thermodynamics say "No!" and that's all you need to know.  We can say with utter, 100% confidence that there is no point in tracking down the specific flaw in the idea.  It's there somewhere and we don't need to look further.  SteveBaker (talk) 01:56, 26 January 2009 (UTC)
 * By the way, if you could actually manage to construct such a tube, you could use it as a space elevator. Most of the strength required of a space elevator cable is to support its own weight.  That's the major stumbling block at the moment preventing anyone from actually doing it.  Sp in ni  ng  Spark  00:38, 26 January 2009 (UTC)
 * (Actually - the current 'fatal flaw' is the modes of oscillation of the cable. A month or two ago it was proved that the cable would have fundamental instability issues that seem right now to be insurmountable without actively positioning rocket motors at many places on the cable - which would make it less effective than conventional rocketry.  It's a serious blow to the future of mankind in space.SteveBaker (talk) 01:56, 26 January 2009 (UTC))


 * This was proposed as a thought experiment, and real world application was never the intention. I was just curious what the effect of the communicating vessels (es:Vasos comunicantes, de:Kommunizierende Röhren) would be.  (The Spanish page actually has a nicer picture).  I would not expect the specific properties caused by a U bend to have any effect if both ends end in space.  If you had one end being shorter than the other though you should get different forces working on both sides and the liquid attempting to reach an equilibrium.  Since Spinning Spark pointed out that atmosphere leaking out would not happen. Like in a Barometer you would get liquid pouring out till the pressure of the air on the short end would be the same as the sum of gravity "pulling down" on the liquid and the vacuum pulling it up in the other leg. But what would the influence of the vacuum be?   Would you get a vacuum /near vacuum somewhere in the middle of the tube or would the liquid "stretch out" to fewer and fewer atoms per volume all the way up to space?  Could we move the space elevator question to a separate item, please?  Otherwise this item will get lost in Carbon nanotube feasibility and other unrelated stuff.  (What happened folks? This is the first I've seen here that everyone seems to agree that pondering the specifics isn't worth the bother of explanation. :-( Everyone too tired?) 76.97.245.5 (talk) 04:53, 26 January 2009 (UTC)

power available from daylight
what is the power available from simple daylight say per square metre - i am aware that this will be a variable amount due to all the variabilities of geography-inclination-time of day-etc. as an instance i have a calculator that provides sufficient electrical power from light to run the electronic circuits and display module.Superbigleo (talk) 16:48, 25 January 2009 (UTC)
 * See insolation. --Tango (talk) 17:08, 25 January 2009 (UTC)

Gluten question
Does textured soy flour contain Gluten?Vanatthelake (talk) 17:36, 25 January 2009 (UTC)


 * No &mdash; the Soyfoods Association of North America says that soy flour and textured soy flour are gluten-free: . TenOfAllTrades(talk) 22:16, 25 January 2009 (UTC)

Cosmic gods
Einstein spent a good deal of his life working on a Unified Field Theory in which he tried to reconcile the four fields we know of. If there were such a thing as a cosmic god who could turn out a "viable" part of the universe by selecting basic features for his creation from which all physical laws would follow as a consequence, what would such basic options be? 196.2.124.248 (talk) 18:04, 25 January 2009 (UTC)


 * Once you accept that God is messing with the laws of physics, then anything you can imagine is possible. This is the problem, actually, as it stops any need to figure out why things are they way they are (that would be science), if you can just say "that's the way God wanted it to be". StuRat (talk) 18:31, 25 January 2009 (UTC)


 * Only if one assumes an arbitrary and personified God, which is not what Einstein envisioned with his "Cosmic Religion", and not what most physicists postulate when they assume there is a divine order to the universe (which many believe in). --98.217.14.211 (talk) 23:11, 25 January 2009 (UTC)


 * Are you asking what is the simplest set of physical principles from which all known physical laws follow as a consequence? The answer is we don't know. Current physics is as simple as we know how to make it (pretty much by definition). -- BenRG (talk) 18:52, 25 January 2009 (UTC)

Even the gods must work within their limitations, so that the menu of permissible options is probably quite small (look what can happen with 100 odd elements, themselves logical consequences of simple arrangements, or just 5 nucleotides or 26 letters and a bit of punctuation). I think that a spartan elegance must be high on their list of priorities. 196.2.124.248 (talk) 21:07, 25 January 2009 (UTC)


 * Your cosmic gods aren't looking closely enough!
 * up,down,top,bottom,strange,charm
 * electron,tau,muon,
 * electron-neutrino,tau-neutrino,muon-neutrino,
 * a couple of weak-force bosons,
 * the gluon and the photon
 * and maybe we'll toss in a higgs boson or two.
 * The menu contains just 18 things - six quarks, six leptons and probably six bosons...and that's all ya need!
 * But then perhaps even that is too complicated and maybe we'll go with nothing more than a simple pan-dimensional vibration.
 * SteveBaker (talk) 23:07, 25 January 2009 (UTC)


 * You're basically asking the question that physicists have been asking since the 1980s—why are there X numbers of things and no more? Why are the values just such? Is there a reason? Can you reduce all of the possible variations of physics down to a few options, and can you find a theory which explains why those options had to be what they were and nothing else? The answer might be "yes", it might be "no", and it might be "we'll never know". --98.217.14.211 (talk) 23:11, 25 January 2009 (UTC)


 * There are 'levels' of power your cosmic gods might have - and the answer depends on where that 'level' is. If I had to invent my own degrees of omnipotence scale:
 * Level 4 gods: Who can do things with technology that almost nobody can understand...yet falls within the bounds of 'known science'.
 * Level 3 gods: There is the "any advanced technology is indistinguishable from magic" kind - where all you get to play with is the laws of physics and nature of matter that pertain to our universe - but with a complete knowledge of all of those laws.
 * Level 2 gods: There is the ability to change the fundamental constants for which we have no real explanation (things like the charge on the electron and the speed of light).
 * Level 1 gods: There would be the ability to change the equations that define the 'rules' of the game - so maybe changing gravity to work on the square of the mass instead of the mass.
 * Level 0 gods: Then there is the kind of power that's hinted at in Carl Sagan's "Contact" (the book - it's not mentioned in the movie) where analysing the expansion of 'pi' as binary digits reveals a message embedded in the bits of the number...which decode to an image of a circle...implying that some "alien" or "god" put it there deliberately for us to find.
 * Each level produces a new degree of incomprehensibility on our behalf.


 * We've "proved" that pi is what it is from raw thought alone - we don't have to measure anything - just have the concept of a circle clearly in mind...and pi just pops out. It just "couldn't" be different.  I maintain that this provides fundamental limits on the power of any god - which is why the idea of a christian 'level zero' god is tough to swallow!  Level 4 gods are mere present day human scientists and technologists - for most humans, understanding how even the simplest childrens' toys really "work" is beyond them.  Level 3 are credible aliens.


 * So if the OP's question has to be answered - we first need to know what degree of power is being envisaged.
 * If our OP's cosmic gods are at level 4 - we know exactly what they can do - because they are out there doing it. It's what most people feel when the new iPhone comes out!
 * At level 3 - we can list many of the laws of physics and particles that these 'gods' have to work with and we can certainly impose restrictions - they can't travel faster than light - they can't travel in time - they can't make perpetual motion machines.
 * If the OP's gods are at level 2 - we've thought about what the universe would be like with different fundamental constants - and mostly we deduce that life could not exist if many things were much different - so our gods don't have a whole lot of wiggle room to change things without totally screwing everything up - butthe consequences of even the tiniest of change would probably produce profound effects that it's hard for us to predict. However, I think we could figure out (at least in principle) what that would do to the universe.
 * At level 1, we're in deep trouble. Understanding what it would mean - even conceptually - to have fundamentally different laws of physics would be tough.  So we can't answer the OP's question.
 * And at level zero...there is no way to even form the thought of what the universe would be like if pi was 10% smaller. Truly omnipotent gods are meaninglessly unfalsifiable.
 * SteveBaker (talk) 01:48, 26 January 2009 (UTC)
 * I'm sure for some decoding mechanism there's an image of a circle embedded in the digits of pi. Level 0 gods would have some pretty staggering powers that approach paradoxical.. for one, the pi thing reminded me of this: take a deep breath and dive into it. How can that pi-encoded message even exist without some kind of decoding context? Could a level 0 god create such a message? I'd say no, but it has to be able to by definition, so that seems to imply the non-existence of a level 0 god. Could a level 0 god create a formal system not subject to the constraints of Godel's theorem? It's been proven impossible; what does that mean for a god that has to be able to do it? Of course this could all be subject to the constraints of our reason (including the maths we have proving it's not, heh)... this is all rather stale argument .froth. (talk) 23:10, 26 January 2009 (UTC)
 * It is conjectured that pi is normal, which would mean any possible message will be included somewhere in the digits. I think the idea behind Steve's "Level 0 god" is that they aren't even constrained by our concepts of logic, which makes it impossible for us to even contemplate them - they are impossible as far as we can tell, but they exist on some level beyond the ability of our logic to make sense of. Don't think about it too much - it will make your head explode. --Tango (talk) 01:03, 27 January 2009 (UTC)


 * Yes - actually, I had already realised that many years ago. There is indeed a perfect image of a circle embedded SOMEWHERE in the infinite digits of pi - because there are only so many patterns of digits possible and all of them must come up sooner or later.  After I read the book ("Contact" by Carl Sagan) - I downloaded the longest available expansion of pi (which was then about a billion digits as I recall) and set about converting it to binary (non-trivial on a computer with less than a gig of RAM!) and looking for the largest square of zeroes with an acceptable approximation of a circle of 1's within it.  My program crunched for about a month - and then another month looking for a circle of 0's in a sea of 1's.  Within the first billion or so digits, the biggest such circle is only about 5 pixels across - and it's a huge stretch to call it a "circle". &lt;sigh&gt;  It would have really screwed with people's heads if I had found one.  But realistically, the probability of even an 8x8 pixel 'perfect' circle is the probability of a specific sequence of 64 consecutive bits having a specific pattern - and the odds of that happening at random is one in 16,000,000,000,000,000,000 - so we need at least 1018 digits of PI before we'll see even a circle the size of this letter 'o' popping out.  Since that's vastly more memory than all of the computers on earth put together - the odds of ever seeing that circle is tiny.


 * So that (in some way) validates Carl Sagan's idea. Now, the message of the book is that science and faith both matter...or something like that.  But, to quote from our article: "Ellie...computes the digits of π to record lengths and in different bases. Very, very far from the decimal point (1020) and in base 11, it finds that a special pattern does exist when the numbers stop varying randomly and start producing 1's and 0's in a very long string. The string's length is the product of 11 prime numbers. The 1's and 0's when organized as a square of specific dimensions form a perfect circle.".


 * Well, the probability of what Ellie finds is actually suspiciously close to my estimate of it being pure chance - so perhaps Sagan has a hidden message BEHIND the message that most people read into the book - which is his old (and much quoted) claim that "Extraordinary claims require extraordinary evidence" may apply here. So perhaps he's hidden a message within his book - "Don't accept some wild-assed claim of there being a circle embedded in PI as evidence of there being a level 0 god out there - this could easily happen by chance alone".  Sadly, the movie flushed away the hook in the tail of the story - it doesn't mention anything about PI or circles and punts for an easier ending.


 * But the probability of a sizeable circle image showing up inside PI as a matter of chance within the digits we're ever likely to be able to calculate is effectively zero (calculating 1020 base-11 digits is far beyond what Ellie could do with the technology available to her) - so if it DID happen within the pathetically few digits we actually have to hand - we'd have to suspect some bizarre supernatural connection. However, these supposed "level 0 gods" don't ever seem keen on providing irrefutable proof of their existence...which is a shame because life on earth would be a lot simpler if they did! SteveBaker (talk) 16:06, 27 January 2009 (UTC)
 * The normality of pi is still just conjecture, so we can't be certain such a sequence will exist somewhere. Pi could be the sequence we've calculated so far repeated indefinitely with an ever increasing number of zeros between each repetition. If it is, that would be far more interesting than it being normal! --Tango (talk) 16:27, 27 January 2009 (UTC)
 * On the other hand, pi encodes the idea of a circle in all of its digits; why look for visual patterns in our arbitrary decimal-expansion of it when we already know circumference = (pi)(diameter)? And decimal expansion really is arbitrary; how do we know the gods don't use roman numerals or one scratch in the dirt for every item counted? .froth. (talk) 18:39, 29 January 2009 (UTC)

Truly omnipotent gods are incomprehensible and postulating their existence raises the age-old logical paradox of how they came about. So quite possibly one of the options that may be tickable, may be the causality/arrow of time feature. 196.2.124.248 (talk) 06:21, 26 January 2009 (UTC)
 * The trouble is that even 'level 3' gods (on my scale, above) are capable of manipulating your thoughts (heck, even us level 4 types get a shot at doing that). So you believe in L3/2/1/0 gods then you don't know what you do or don't know because the god(s) may be tampering with your thoughts.   That's one of the things that makes them unfalsifiable.  I say "God doesn't exist because I've managed to prove 'X'."...and you say "Aha! That's just because he wants you to think 'X' in order to test your faith."...so it's worse than "incomprehensible" - it's "meaningless - even in principle - to discuss it".  At which point we wield our mighty 'razor of Occam' and end the speculation right there.  SteveBaker (talk) 19:17, 26 January 2009 (UTC)
 * That's why religions often (always?) introduce the concept of "free will" even though their god(s) certainly have the power to influence our thoughts. Without free will, it just becomes impossible to have any meaningful theology. (Also, people like to feel in control - although, interestingly, they rarely like to actually be in control.) --Tango (talk) 19:45, 26 January 2009 (UTC)
 * While riding rollercoasters people like to be safe but dont like to feel safe. Sort of the same thing with control sometimes .froth. (talk) 00:34, 27 January 2009 (UTC)


 * To answer that - you have to realise that what god(s) say is mostly known because that's what the priests say. If people don't believe that have free will then if they screw up, it's God's fault.  That's not good.  Now people can (in practice) do what they heck they like and blame their local gods...and the priests can't do a damned thing about it.  The priesthood lose power over the populace and it's all over for religion within one generation.  On the other hand, if you are responsible for your own actions - then if you screw up, the priests can point out how the god(s) aren't going to be happy with you and you'd better sort out your behavior or you'll be banished to hell for eternity.  This is an effective way to get your populace to knuckle under and do what the priests claim is god's will (and which, incidentally, allows them to carry on not having to do their share of the cleaning the cow shit out of the barn). SteveBaker (talk) 00:38, 27 January 2009 (UTC)


 * Watch out when people are under threat of social censure or eternal banishment and a convenient scapegoat is around.. Puritans believed that every little thing happened as a result of blesssing and punshment for the righteous and sinful.. if a cows milk is discolored, either the farmer sinned or SHES A WITCH! .froth. (talk) 00:50, 27 January 2009 (UTC)


 * With our current understanding of quantum mechanics, I don't think we can talk about "supernatural" as breaking the law of physics. It would be more correct to say, breaking the "law" of probabilities. And that "God is messing with the laws of physics" might as well be better described as god leaving the laws of physics alone, and messing with probability alone. At quantum level everything is possible (teleportation, quantum entanglement, etc.), on higher level it's still possible, but so unlikely we're almost sure it'll never happen. --131.188.3.20 (talk) 12:16, 28 January 2009 (UTC)
 * I <3 the refdesk. ReluctantPhilosopher (talk) 11:57, 30 January 2009 (UTC)


 * I'd like to add a level -1 to Steve's list:


 * Level -1 gods: the Superlogical god, or "God beyond logic": able to make contradictions true, like to change the value of pi, and not to change it in the same time. Or: create a stone so big that he is not able to raise, and at the same time, to be so strong to raise it. Such a god can easily bypass every contradiction that we invent to prove that he does not exist. He is also able to exist and not to exist in the same moment. Note: although this level is very difficult to achieve for a standard god, apparently, it is exaclty what all of them would like to be -- and humans also, when they happen to gather too much power :(  --pma (talk) 14:42, 21 February 2009 (UTC)

mt st helens
Hi, I am investigating the eruption of Mt StHelens as part of my geography project.Is there a web address of the local newspaper from that area where i could learn first hand the timeline of the eruption? Thanks Quinnp (talk) 18:19, 25 January 2009 (UTC)


 * This was a national event, so you don't have to limit yourself to local sources for info about the timeline of Mount Saint Helens. See 1980 eruption of Mount St. Helens, which has many references at the bottom, and also contains a rough timeline. StuRat (talk) 18:28, 25 January 2009 (UTC)


 * http://www.oregonlive.com/oregonian —B00P (talk) 21:05, 25 January 2009 (UTC)
 * National Geographic. Twice, once soon after eruption and once a year or so later. Polypipe Wrangler (talk) 03:11, 27 January 2009 (UTC)

Which lightbulb?
Hi. Can anybody help me identify this lightbulb, please? As you can see from the picture it is just over 30mm long and is used in a 6 bulb "chandelier" light fitting, which is the main source of illumination in a room measuring 6m by 6m. Thanks CCorncob (talk) 18:51, 25 January 2009 (UTC)
 * Looks like some sort of halogen bulb. DuncanHill (talk) 20:21, 25 January 2009 (UTC)

I have managed to find some more info on one of the bulbs, that can be seen here. Not sure if it is helpful. Thanks CCorncob (talk) 21:30, 25 January 2009 (UTC)
 * I can make out "12V20W" on the bottom line of writing, this means that it is a 12 volt, 20 watt bulb. If I recall correctly these are quite common - your local hardware shop should have them if you need a replacement. DuncanHill (talk) 21:35, 25 January 2009 (UTC)
 * The letters "FSL" appear to be a trademark of Foshan Electrical and Lighting Co., Ltd. I think it is a G4 fitting (is it 4mm between the contacts? If so, it is a G4). DuncanHill (talk) 21:59, 25 January 2009 (UTC)
 * Yes the spacing is 4mm, so thanks for identifying them. I have seen these bulbs, but the contacts seem a bit thicker. Do you think they would still be appropriate? Thanks again. CCorncob (talk) 00:08, 26 January 2009 (UTC)
 * Probably, these things tend to be pretty standard. DuncanHill (talk) 00:10, 26 January 2009 (UTC)
 * OK great, thanks again for your help. CCorncob (talk) 00:18, 26 January 2009 (UTC)
 * If it's a 12v halogen - it's probably some variety of car headlamp bulb that they've adapted for this use. SteveBaker (talk) 00:53, 26 January 2009 (UTC)
 * They are used a lot in desk lamps and the like - I've just realized that the lamp on my computer desk uses one. DuncanHill (talk) 00:55, 26 January 2009 (UTC)


 * I have a set of these in some low-profile "hockey-puck" style lights I use around my house in a few applications. The local supermegahardwarestores (here Home Depot and Lowes) both carry LOTS of these kinds of bulbs in various sizes.  Just take the bulb to the store and match the shape/size/markings.  That's what I usually do.  --Jayron32. talk . contribs  04:56, 26 January 2009 (UTC)

Identifying a street light bulb
So, the question above reminded me about this. The street light outside our kitchen window went out a month or two ago, and the bulb was replaced by some different kind. The light is quite blue-violet, making the white walls and the snow outside look bluish. When starting up, it starts out reddish, and then gradually moves over to the bluish color, in... say, 20-60 seconds. It seems to be pretty high-intensity, lighting a pretty large area. Any ideas what kind of lamp this is? The more important question is, though: do they flicker (like some fluorescent light bulbs)? -- Aeluwas (talk) 19:12, 25 January 2009 (UTC)
 * Possibly a mercury vapor bulb =- Nunh-huh 19:55, 25 January 2009 (UTC)
 * Or maybe a LED street light. Clarityfiend (talk) 20:03, 25 January 2009 (UTC)
 * No - it can't be LED - they don't shift color. SteveBaker (talk) 20:19, 25 January 2009 (UTC)
 * Egad, I've been LED astray. Clarityfiend (talk) 20:49, 25 January 2009 (UTC)

Water Clock Thingie Question
I am trying to build a water clock. My plan was to use a graduated tube and a valve and then have the valve drip at a constant rate. Then, i would measure how much water had drained and (using a graph) would be able to tell about how much time had passed. Unfortunately, after 30 mL have drained, the rate slows significantly. The articles i have read about water clocks say they use sloping sides. Does this help keep the flow constant? and if so, how could i change my plans to make it work accurately? Should i change from a straight tube to a funnellike tube? Any help at all would be appreciated. Buffered Input Output 20:28, 25 January 2009 (UTC)


 * Using odd-shaped tubes doesn't change the rate at which water flows out - but it does change the rate at which the level in the container falls when a given volume of water has flowed out. So if you pick a container whose cross section at every height is proportional to the rate of flow when the water is exactly that deep - then the rate that the water level falls is more or less uniform even though the rate of water flow changes.  Getting exactly the right container might be tough though - so for a practical project, you might want to look at other ways.
 * One other way I could think of to do it would be to graduate the time scale non-uniformly so that the distance between the marks indicating that the first minute has elapsed are further apart than the ones indicating the last minute...that makes it harder to read off the time - but at least then you can use a cylinder.
 * Another idea that comes to mind is to have three containers at different heights. The one at the top supplies water by pouring it into the second.  The rate of flow into the second container is designed to be higher than the rate water drips out of it - so it always overflows into a suitable outlet.  This wastes water but ensures that the second container is always 100% full - so the pressure inside doesn't change and the flow out of it is precisely constant.  Sadly, because the water level in the second container never goes down - you can't use that level to tell the time...but you CAN catch the water that comes out of a spout to fill up a third cylindrical container and use the level in THAT one to tell the time.
 * There are lots of other ways. SteveBaker (talk) 20:52, 25 January 2009 (UTC)


 * While the above approaches work for a few hours (or days using large enough tanks), you might need an automatic method of refilling the tank to make this a permanent clock. The method used in a toilet tank, with a float valve which connects to a tube of pressurized water, is probably the simplest. This still allows the tank volume to vary somewhat, so the drips won't be exactly constant, but you can just average the length of time between drips and use that.  Another approach is just to use a dripping faucet, which, being connected to a constant water supply, should only vary if the pressure changes. StuRat (talk) 01:58, 26 January 2009 (UTC)
 * Of course - all clocks need a source of power - and that might well be a natural stream or river. But the idea of a constant-pressure tank that's allowed to overflow (with the overflow flowing away someplace) is a really simple way to get constant pressure with the primitive means available to water clock designers.  The only real problem is the waste of water - but if you're feeding fountains and such it's a very small deal.  The flow rate into the constant-pressure container only has to be a tiny percentage more than the clock's 'useful' outflow rate - just enough to cover the variability in pressure of your ultimate waters source.  Kinda like we use zener diodes to limit voltages for our electronics.  We are always using the hydraulic analogy to describe electronics - well, you can reverse the analogy to make a water clock using the ideas from electronic clocks! SteveBaker (talk) 02:19, 26 January 2009 (UTC)

Our article on water clocks has some OK descriptions of some ancient designs and it is also QUITE well referenced with some external links and books. You may find some good information starting there and taking it where it leads you. --Jayron32. talk . contribs 04:53, 26 January 2009 (UTC)

I'm sorry i wasn't really clear on my question. My question was if i NEED a sloped-side container to make this work with some degree of accuracy. Buffered Input Output 13:48, 26 January 2009 (UTC)


 * Then no, you don't . StuRat (talk) 17:04, 26 January 2009 (UTC)

Definition of Work
Why is work defined as Fd and kinetic energy as 1/2 mv^2? Why not use work=2Fd and KE=mv^2? Is it simply because Fd is more concise than 2Fd, or is there a better reason? --99.237.96.81 (talk) 23:00, 25 January 2009 (UTC)
 * It seems to be a matter of how the units of work and energy are defined. If force is mass times acceleration, then in the metric system it can be given as kilogram meters per second squared. Then force times distance is kilogram meters squared per second squared, which is the definition for Newtons. You could have measured force in a new unit called "figs" where two "figs" equals 1 Newton, and then force would be 2Fd. Edison (talk) 23:10, 25 January 2009 (UTC)
 * You are right that it is a matter of definition. However, it is not the units, but rather the quantities. In most areas of physics, formulas don't change with the change of units. Velocity, for instance, is always simply distance/time, no matter if you use meters, kilometers, or miles for the distance and hours or seconds for the time. (To avoid using higher math, I used the formula for no acceleration.) The situation is rather like that of a circle. We know that the circumference is equal to 2πr, where r is the radius. If you don't like the factor 2 there, just use the formula πd, where d=2r is the diameter. &mdash; Sebastian 23:38, 25 January 2009 (UTC)


 * Suppose that I don't change the units of measurement. I'm under the impression that although Fd=(1/2) mv^2 can be derived from Newton's second law, work and kinetic energy are equal to Fd and (1/2) mv^2 only by definition.  If that's the case, why can't I multiply both sides of Fd=(1/2) mv^2 by 2, call the left side "work", and call the right side "kinetic energy"?  The units are still consistent; just as multiplying the diameter of a circle by pi doesn't mean a new unit has to be invented for the circumference, 2Fd can still be measured in kilogram meters squared per second squared.  --99.237.96.81 (talk) 23:32, 25 January 2009 (UTC)


 * Yes, you could build a system based on what you suggest, but it is not very useful. Putting aside the issue that $${1 \over 2} mV^2$$ is only an approximation in the first place, and there are higher order terms if relativistic effects are considered, you will still cause problems.  You will be building a factor of two into all sorts of equation, many not obviously related.  For instance, it will affect the definition of electrical potential difference which now becomes $$- 2\int E \cdot dl$$ instead of $$- \int E \cdot dl$$, unless of course, you change the definition of the volt, but then you will have to mess with equations like $$P=IV \,$$.  This factor of two is a dimensional constant.  The SI system has gone to great lengths to eliminate as many dimensional constants as possible from the system of units.  Before then engineers and scientists were required to remember a great number of them.  It is a step backwards to start putting them back in.  Sp in ni  ng  Spark  00:11, 26 January 2009 (UTC)


 * This is kinda silly - you can do this with almost anything. If I decide to measure distances as the "extent as measured from the midpoint" instead of from one end to the other (analogous to measuring the radius of a circle rather than its diameter) - then you end up with velocity being twice the "distance" divided by the time (v=2d/t).  To get rid of the 2 you can choose to redefine the meaning of velocity - but you then need to go off and fix a bunch of other things...2's and 0.5's pop up in some places - and disappear in others.  Some equations will get more complicated - others will get simpler.  I suspect (because we've been doing this for a LONG time) that overall things would get more complicated.  But we don't fundamentally gain or lose anything - no additional insight results.  We happen to have picked one 'meaning' for work, force, energy, etc - you COULD pick a different one - but that just causes everyone to have to reprint an awful lot of textbooks.  You can see this happening in all sorts of areas of engineering where a factor of 'g' (9.8 meters per second per second) creeps in to simplify equations that involve 'weight' rather than 'mass'.  The result is generally a lot of confusion...so we work hard not to do that. SteveBaker (talk) 00:51, 26 January 2009 (UTC)


 * OK, so a joule is defined as "work done by 1 N over one meter". If energy is discussed in the context of thermodynamics, relativity, quantum mechanics, or anything else, one joule has to be the equivalent of 1 N over one meter.  Is that correct?  --99.237.96.81 (talk) 01:49, 26 January 2009 (UTC)


 * The definition of the unit doesn't change - but you have to be careful because in the context of things like relativity, measuring things like mass, length and time gets tricky - and lots of our basic equations of dynamics and energy are simplified Newtonian equations that are only approximations when you start to consider relativistic objects. At the quantum level, everything gets kinda fuzzy - so again, the definition of what a Joule is doesn't change - but the ability of objects to not be in one place makes measuring properties and plugging them into fundamental equations really tricky.  This is dangerous territory for 'armchair physicists'! SteveBaker (talk) 02:10, 26 January 2009 (UTC)