Wikipedia:Reference desk/Archives/Science/2007 July 5

=July 5=

SpaceShipOne Orbit Style
Could Rutan's method of lifiting spacecraft then launching them into space be used to achieve orbit? Does his engines, if scaled up, a bit meet the requirement for reaching orbit or would diffrent kind of engines be needed?67.121.105.12 02:04, 5 July 2007 (UTC)


 * No physical law precludes that approach. It has yet to be seen whether the engineering and financial challenges can be feasibly and safely overcome.  Among the major challenges are control and stability, and carrying enough fuel. Nimur 03:06, 5 July 2007 (UTC)


 * The idea has been floated a number of times, both in science fiction and real life. Using an airplace in lieu of a first stage makes reusing the first stage quick and easy (in principle) and it means that your rocket will start out with significant speed and altitude, as well as above much of the atmosphere and weather.  (The idea of using a balloon to get above a lot of the atmosphere has also been proposed; it was even used for suborbital sounding rockets in the 1950s: see rockoon.)
 * This page has a list of air-launched rocket craft (proposed and flown). The Soviet Union developed and tested an air-launched spaceplane (called MAKS), but the program ended with the Cold War, and it never reached orbit: . TenOfAllTrades(talk) 13:23, 5 July 2007 (UTC)
 * Some of the X-planes were launched that way - and many of them reached "the edge of space", so SpaceShip One was hardly the first. Rutan certainly claims to be able to reach orbit with a similar approach to his first effort - and he's a pretty smart guy, so I'm inclined to believe him.  My best guess is that his approach to re-entry is his biggest problem.  SpaceShip One only just got out of the atmosphere - so that on re-entry it was moving rather slowly and managed to cope without needing fancy heat tiles or ablative coatings.  When you re-enter from orbit, you've been falling for a long time without air resistance by the time you hit atmosphere - so your speed is much greater and slowing down becomes a major problem.  SteveBaker 14:16, 5 July 2007 (UTC)
 * The Pegasus rocket from Orbital Sciences is a commercial satellite launch system that is launched from a modified commercial airliner. They have launched quite a few satellites. -Arch dude 02:53, 6 July 2007 (UTC)
 * Wow! Interesting!  They do say though that the primary reason for the air launch has nothing to do with getting the thing up high and going fast at the point of the launch - they do it to save on the cost of ground-based launch failities and to avoid launch delays due to bad weather.  That's a fascinating thing!  Thanks for the link. SteveBaker 20:23, 7 July 2007 (UTC)

ultrasound???
hey friends is anyone having idea about the ultrasound machine: 1.consumption according to a particular frequency generation. 2.minimal space requirement for specifc 20,000hz machine.

please help in urgent need

Sameerdubey.sbp


 * SameerDubey, with all due respect, I can't tell what you are asking. You might be interested to know that 20 kHz is probably not ultrasound, since it is approximately in the range of human hearing (on the high end, so it may be barely out of audible range for many people).  A machine would consume energy (probably electrical energy), and would most likely be an ultrasonic transducer.  Nimur 06:50, 5 July 2007 (UTC)
 * Agreed - Ultrasound is more often in the MegaHertz (MHz) to GigaHertz (GHz) range - but unless we know what it's for - we can't answer either question. It's not just about the frequency - the power required and the way it's going to be used and the way that results are collected and displayed at much more relevent!  The ultrasound units used for checking the health of unborn babies are totally different from the units used to detect cracks in welded steel which in turn are completely different from the ultrasonic cleaning bath I have at home for cleaning gunk off of old car parts. SteveBaker 14:06, 5 July 2007 (UTC)
 * Even ~30 or 50 kHz is usually called ultrasonic, but 20 kHz is probably not. Nimur 17:31, 5 July 2007 (UTC)
 * Hmmm - well I wouldn't have said so - but our article on Ultrasound says 20kHz. Weird. SteveBaker 19:12, 5 July 2007 (UTC)
 * Short of an ANSI or ISO standard, there's not going to be a well-defined border for the nomenclature. But if professional audio is anything to gauge, it is extremely common to have 44.1 kHz and 48.0 kHz recordings - which would indicate a folding frequency at 22.05 and 24 kHz, respectively.  That, to me, suggests that there must be some audibly discernible signals at those frequencies.  I worked with a SONAR system for a while that operated at 34 and 70 kHz, and it was most certainly ultrasonic; but it also produced some unwanted harmonics (undertones?) that could be heard as mild, faint buzzing.  (The system was operating at 100+ dB in the ultrasonic range...) Nimur 21:15, 5 July 2007 (UTC)

Satisfaction of Swallowing
Why is it that we must swallow food to enjoy it? I tried "eating" ice cream by savoring the food, then spitting it out and chasing it with a spoonful of rice. My stomach picked up on the bait-and-switch and I was not satisfied. Why does swallowing the food complete the satisfaction effect? If this weren't the case, it would be much simpler for people to not gain wait brought on by heavy foods. H YENASTE 05:03, 5 July 2007 (UTC)


 * Evolutionarily, we want to swallow food because only then can we begin the digestion process to extract nutrients and fat from it. It's only in the modern world that we eat so much high fat foods that we want to lose weight, our body systems havent caught up with the modern world. We get very little nutrients from food we don't swallow. 213.48.15.234 06:46, 5 July 2007 (UTC)


 * It is our stomach that tells us when we are satisfied. Check out the articles on hunger and appetite.--Shantavira|feed me 10:38, 5 July 2007 (UTC)


 * Yes, but the OP asked why they couldn't spit out ice cream and substitute rice. This should satisfy the stomach, while the ice cream satisfies the tongue.  The Question is "why didn't this work?" I would say that most likely, the ice cream contains something which your body craves that the rice does not.  For instance, plain rice is low in fat.  I would suggest that you try eating just a little bit of ice cream maybe a couple of spoons to fool the stomach then starting the bait and switch with the rice.  Let us know how it works for you. - Czmtzc 15:02, 5 July 2007 (UTC)


 * I guess the problem is that enjoying the taste of something - and having your hunger satisfied are two completely independent sensations. What we want from food is a combination of both things.  It's possible to taste ice cream without swallowing it (well, technically: "you can if your willpower is a lot stronger than mine"!) - but I think it would be hard to swallow enough rice without tasting it along the way.  So I think the reason you aren't happy with the experiment in an overall way was not that the rice didn't satisfy your hunger - but that it was boring to eat and even the occasional mouthful of ice cream didn't help that.  It's a hard experiment to do well because the only reasonable way to get the bland food into your stomach is going to involve tasting bland food.  I wonder about chewing gum though...hmmm.  I admire your efforts to employ good scientific methodology though - everyone should do more to experiment with the things around them! SteveBaker 15:16, 5 July 2007 (UTC)

Food For The Homeless and $1,000,000
I have been discussing a question with a friend of mine for quite some time (~1 month). I have my ideas, he has his; I wanted to see what the Wikipedia Refernce Desk community could come up with. This is in no way a ultra-precise or "nit-picky" question.


 * Let us imagine that you have $1,000,000 cash.
 * You want to feed the maximum number of American homeless people possible using this money.


 * What should you buy? White Rice? Cans of Meat and Beans? "For Maximum Value"-Brand Cheerios?
 * What is the healthiest, but cost effective (read: dirt cheap) food to buy?
 * About how much of it would you be able to purchase? How many people would it feed?
 * The costs of delivery to the homeless people is not a factor - they must come TO your food stockpile to recieve the food.


 * --67.177.170.96 05:40, 5 July 2007 (UTC)


 * Just to add onto the question above, would it be more effective to buy land and seed and fertilizer and to grow the food? 213.48.15.234 06:48, 5 July 2007 (UTC)


 * One million dollars isn't really a lot of money. But first, you should evaluate some philosophical choices - is it better to feed a small amount of people for a small number of meals ( ... buying a full lunch for a million people), or to feed a few people many times (buy a year's supply of food for 500 people)?  What level of cost-nutrition tradeoff are you willing to accept?
 * In any case, it may be easier to imagine the cost-per-meal. If you are an effective negotiator, you can probably buy bulk ingredients at cost.  How "raw" you go will determine how much preparation and labor you need to turn it into a meal.  But if you could get the ingredients down to ~$1 per meal, (say, a peanut butter sandwich on two pieces of bread; a carrot, and a glass of juice), you could feed 1,000,000 people one small meal.  It is not even clear that there are this many homeless people near enough to walk to your sandwich depot, but census numbers vary wildly for that demographic (these statistics indicate that 13 million Americans (7.4%!) self-identify as having been homeless at some time, while conservative estimates place the number much much lower).
 * But this leaves you with a nasty predicament. This hypothetical solution has fed a million people one meager sandwich, and now they are off again on their own.  The contribution to their health is debatable; only a very minuscule percentage would have starved if not for your sandwich contribution.  Those who would have starved may not be much better off anyway, because you have only given them one meal (enough food to last another few hours?)
 * It would make significantly more sense for you to prioritize how hungry people have to be, and give them aid based on that level. But that will require a bureaucracy, a lot more labor on your part, and you may have to make a few gut-wrenching decisions between who gets to eat and who may not.  Nimur 07:02, 5 July 2007 (UTC)


 * You could invest the million dollars, reinvest enough of the profits to keep up with inflation, and spend the rest of the profits on food. This way you would have a steady inflow of money. —Bkell (talk) 07:11, 5 July 2007 (UTC)


 * Surely what the homeless need is housing. Anyway, the best investment would be to buy lots of fishing rods and teach them to fend for themselves.--Shantavira|feed me 07:43, 5 July 2007 (UTC)


 * The problem is much more complicated. Firstly, you need to think about transportation.  There is very often excess food produced in the more fortunate parts of the world that could be had for $0 (I was listening just this morning to an NPR report that European grape growers are being paid to destroy part of their crop because of the effect that over-production is having on price) - but getting those excesses into the right place is a big issue - perhaps your best use of that $1,000,000 is to pay for transportation instead?  Secondly, over what time-period are we talking?  If you take the $1,000,000 and invest it wisely, you'll get a 5% or so return on it - which means that you have $50,000 per year FOREVER.  After 20 years, you'll have helped the same number of people as with $1,000,000 spent all in one lump today - but after 100 years, you'll have done much more good.  Invest the money as micro-finance loans to people in the area and you'll be doing good while you are making that money.  Thirdly, simply giving people food doesn't solve anything over the long term.  If you give them food, they might stop farming and live on the food you provide - that means that when you run out of your $1,000,000 - they may be worse off than when you started.  It would be better to invest that money in improving their food production infrastructure than to provide direct food aid.  (Although, clearly there are emergency situations where immediate short term food aid is both necessary and beneficial).  In the end, to take the ultimate 'long view', the problem is that much of Africa's climate and soil conditions simply doesn't allow it to produce enough food for all of the people who live there - the solution is to have less people.  There is merit in providing funding for long term population control. To answer your actual question - the answer is Rice. SteveBaker 14:01, 5 July 2007 (UTC)


 * Not to mention those pesky civil wars that keep blowing up all the infrastructure that endemic corruption even allow to be built in the first place. As for the OP - white rice is less nutritious than the whole stuff, but SteveBaker I believe is correct in suggesting rice as *the* answer for a single staple to feed the masses, although I seem to recall that bananas put in a pretty good showing if you do not have to worry about spoilage. Consider the rolling population explosion across southeast Asia as rice cultivation spread, and then factor in all the breeding and other genetic modifications (e.g. golden rice) that have happened since. As for pricing your solution, a lot depends on how much volunteer labor you can mobilize to cook for you, as processing adds to food costs. -Eldereft 07:48, 7 July 2007 (UTC)

The $1M would be best spent shipping them over to the UK, where we don't let people starve or go homeless. Plus they'd get free medical care. 80.2.220.179 23:51, 13 July 2007 (UTC)

Re:Protons, Electrons, Neutrons and such
What produces these charges? Does heat produce electron? If it does, then what does cold produce? How do you know if something is positively charged (protons) or negatively charged (electrons)? And secondly, does lightning come from the ground? Finally, if a car produces a large number of electrons, and the road produces an equal number of static charge, will the car be pushed away from the road? - Zachary crimsonwolf  13:05, 5 July 2007 (UTC)
 * Lightning travels most commonly from cloud to cloud, however what most people think of when you refer to lightning is from cloud to ground. The article does indicate that lightning can also travel from ground to cloud . Lanfear&#39;s Bane

Okay. Thanks for that! Cheers!!! - Zachary crimsonwolf  13:28, 5 July 2007 (UTC)


 * We don't really know what creates charges, they are just a quantum number, an intrinsic property of particles, which determines how strongly they interact with photons, i.e. the electromagnetic field. I'm not sure what you mean does heat produce electrons? Heat in itself doesn't no, but the energy from heat can ionise atoms, that is remove a negative electron, leaving a positive ion. Cold is simply an absence of heat energy, not an opposite so produces nothing. Positive/negative charges can be deduced from the direction of curvature during motion in a magnetic field, or the direction of force in an electric field. Which is positive and which negative is simply a matter of convention, we could equally well swap the names round. The important point is they are opposite charges. Lightning has been covered above. The car question has me confused again! Maybe the simplest thing to say is that electrons are not really produced, simply moved around. If the car gains eletrons from the road somehow (static electricity in effect) it will leave behind a positive road and be attracted to it, not repelled. Charge is conserved, basically moved around not created. Cyta 13:32, 5 July 2007 (UTC)


 * Electrostatics may also be helpful to you. DuncanHill 13:33, 5 July 2007 (UTC)


 * Let's break this up for more manageable answering:


 * What produces these charges?
 * The charge on these fundamental particles is just an innate property of the particle - nothing 'produces' it - it's just a property - like their mass. SteveBaker 13:43, 5 July 2007 (UTC)


 * Does heat produce electron? If it does, then what does cold produce?
 * Heat is just the measure of how fast (on average) the molecules are moving/vibrating. Heating some substances may cause them to emit electrons - see Thermionic emission. SteveBaker 13:43, 5 July 2007 (UTC)
 * To clarify, heating something can cause it to release electrons as opposed to creating electrons. &mdash; Laura Scudder &#9742; 14:51, 5 July 2007 (UTC)
 * How do you know if something is positively charged (protons) or negatively charged (electrons)?
 * You bring something whose charge you know to be (say) positive close to the unknown thing and see if it is attracted or repelled by it. Like charges repel, unlike charges attract. SteveBaker 13:43, 5 July 2007 (UTC)


 * The mathematical and moral definitions of the terms positive and negative don't apply to positive and negative charge, they're just arbitrary polar descriptions of a property. --  JSBillings  14:21, 5 July 2007 (UTC)
 * That's true - but we needed a pair of names with opposite meanings! Physics is full of arbitary names for things - that's how we ended up with Strangeness, Charm, Bottomness and Topness.  One certainly cannot garner extra meaning from the names chosen.  So you can tell whether two electrical charges have the same sign by whether they attract or repel each other - but is you don't have a 'known-to-be-negative' or 'known-to-be-positive' object handy then there is no 'absolute' way to tell (that I'm aware of).  SteveBaker 14:52, 5 July 2007 (UTC)
 * You could look at how the charged object interacts with other EM things...throw it through a magnetic field of known direction and see which way it curves or throw it past a compass and see which way the compass points. But still, need some known starting point. DMacks 17:03, 5 July 2007 (UTC)
 * Or apply a magnetic field to a conductor through which current is flowing and measure curvature via the Hall effect. -Eldereft 08:04, 7 July 2007 (UTC)
 * Right - there are plenty of ways to determine this - but (I believe) that all of them depend on you having something with known polarity (either a positive or negative charge/potential-difference or a current whose direction of flow you know or a magnet for which you know which end is north and which is south). Since we know the polarity of the earth's magnetic field, then a compass needle is one way to get that with certainty.  But how would you tell if you didn't have anything like that? SteveBaker 14:18, 7 July 2007 (UTC)
 * How about ionzing some helium or hydrogen and sending it past a magnet or unknown orientation: positive ions curve one way, negative ones the other. Nuclei are much heavier than electrons for the same amount of charge, so will curve much less, so looking at the curvature tells you the mass (and therefore identity) of that particle. Look at the direction of that particle stream's deflection, now you know the orientation of the magnet. Build yourself a bubble chamber. DMacks 18:48, 10 July 2007 (UTC)
 * And secondly, does lightning come from the ground?
 * See Lightning - it's rather complicated. SteveBaker 13:43, 5 July 2007 (UTC)


 * Finally, if a car produces a large number of electrons, and the road produces an equal number of static charge, will the car be pushed away from the road?
 * Well, if a static charge were being built up on the car by virtue of the tyres rubbing on the road, you'd maybe get electrons building up on the car - and left-over protons on the road (or vice-versa) - this would result in the car being attracted towards the road - not pushed away from it. However, the force would be very tiny indeed and in any case, I'm pretty sure that the static charge that builds up on cars comes from friction with the air - not the road. SteveBaker 13:43, 5 July 2007 (UTC)


 * Many thanks, all! To tell the you truth, its my teacher who told us that heat (somehow) produces electrons. And if you remove the tires of a car while its moving, leaving only the rim, the rims will produce electrons (because of heat). The road produces electrons as well (because of friction, which produces heat), and because of that, the car will (literally) 'fly' because the electrons repel each other. - Zachary crimsonwolf  13:47, 8 July 2007 (UTC)


 * I sometimes worry about how educated teachers actually are. But now you can teach them something. Cyta 07:08, 9 July 2007 (UTC)

Well, the answers certainly had helped me. So..I would like to thank you all again. Cheers!! - Zachary crimsonwolf  09:19, 9 July 2007 (UTC)

Facial hair (from Humanities)
What is record of earl facial hair and late facial hair? --Vess 07:29, 5 July 2007 (UTC)


 * I don't understand your question. Have you read facial hair and Earl "Facial Hair" Derby?--Shantavira|feed me 08:05, 5 July 2007 (UTC)
 * I think they meant early facial hair. WAFFLESOAP 09:28, 5 July 2007 (UTC)

I meant early and late facial hair. --Vess 10:03, 5 July 2007 (UTC)


 * Pituitary adenomas can cause the growth of ancillary and facial hair at virtually any age. These are hormonal variations, and therefore there wouldn't really be a "record."  Instead, there would be various disease states, and those with either the lack of facial hair despite functional male gonads or the presence of facial hair despite the lack of mature male sex hormonal organs would suffer from other symptoms and would be distinctly suffering.  Geogre 11:55, 5 July 2007 (UTC)
 * NO! Pituitary adenomas are extremely unlikely to produce facial hair-- not one in 10,000 cases. This is all nonsense offered by an editor who should know better. alteripse 19:25, 6 July 2007 (UTC)
 * A condition of very early precocious puberty in boys causing early growth of facial hair – possibly as early as from age 1 – is testotoxicosis. Delayed puberty, possibly indefinitely delayed, can be caused by a variety of conditions, including Klinefelter's syndrome and androgen insensitivity syndrome. By the way, a more appropriate spot for this question is the science section of our reference desk. --Lambiam Talk  12:38, 5 July 2007 (UTC)
 * Not facial hair by itself. Advanced precocious puberty may be associated with beard growth in a boy, but only after advanced maturation of the genitalia and bones. alteripse 19:25, 6 July 2007 (UTC)


 * I suspect the original poster may have meant early and late in a historical sense - that is to say, changes in styles of facial hair through history. DuncanHill 12:45, 5 July 2007 (UTC)

I meant without disease. Howewer, by the way, what was the known historical period in which men had early facial hair and what n which they had late facial hair? --Vess 14:47, 5 July 2007 (UTC)
 * Even at birth there is a fine 'peach fuzz' of hair on babies faces - it's just a matter of degree - you're not going to find "WOW! A boy born in transylvania in 1796 had a full beard at age 3." (I just made that up OK!)...because it's just not a clear-cut thing. SteveBaker 14:59, 5 July 2007 (UTC)
 * Closer but still not quite. There are several types of facial hair that are being confused in these answers, and the difference IS generally a "clear-cut thing". The two main categories are vellous and androgenic. Vellous hair is not hormone dependent and is normally present all over the body at all ages but in widely varying densities. There are genetic differences in heaviness, color, and density in healthy people, and sometimes it distresses people from a cosmetic perspective. There are extremely rare cases of defective control of this type of hair growth due to single gene mutations, sometimes familial, resulting in generalized hypertrichosis,-- someone who might get a job as a "wolfman" in a carnival. This condition becomes apparent in early infancy. Exaggerated growth of fine vellous facial hair can also accompany some chronic non-hormonal diseases in childhood (like chronic renal failure), and this too can appear before 5 years of age. This also can occur in chronically malnourished adolescent girls with anorexia nervosa. Lanugo hair is a type of fine hair present in fetal life and would qualify as the earliest facial hair. Androgenic hair is what normally grows at puberty as a result of rising testosterone levels in both males and females. It can occur in childhood as a result of any form of androgen excess but is an advanced, rather than an early manifestation: pubic hair is the first place androgenic hair grows in conditions of androgen excess. alteripse 19:36, 6 July 2007 (UTC)
 * Vellus & Androgenic hair --JWSchmidt 04:40, 7 July 2007 (UTC)

Valence electrons
In most metals (I assume all, but I know someone will find one counter-point) there are electrons that float on the surface of the metal, giving it the metallic luster. Are these electrons called valence electrons or is there another more exact name for them? The article claims that valence electrons are in the outer-most shell and the ones on metal are not really in any shell. They just float on the surface - or is that just an apparent floating from outer shell of one atom to another? -- Kainaw (what?) 16:17, 5 July 2007 (UTC)


 * I'm no chemistry expert, but this is what I figure: That each atom of the metal has its valence electrons, in the outer most shell. But then, between metal atoms, metallic bonding exists, so that metals are held together so to say by a 'sea of electrons', delocalised electrons floating that broke off from valence shells?
 * See the Metallic Bond article, if it helps.74.102.89.241 16:37, 5 July 2007 (UTC)
 * The electrons aren't just "floating on the surface" of the metal, but can move throughout the whole piece of metal (see the metal article for more details about this bonding picture). There are indeed surface effects on metallic materials and other conductors, but the idea of valence electrons is in relation to each atom, not bulk material. DMacks 16:57, 5 July 2007 (UTC)


 * Thanks - conduction electrons is what I was looking for. -- Kainaw (what?) 17:16, 5 July 2007 (UTC)

UDDERS
What happens to wild cows and goats (and the like) when their udders are full? I know this is a dumb question but it has been torturing me for some time now.


 * They stop producing milk. The reason milking cows and goats produce so much milk is because they are milked regularly.  It is an adaptive reaction.  The more they are milked, the more milk they produce.  They less they are milked, the less milk they produce.  By the way, humans function the same way.  See breastfeeding. -- Kainaw (what?) 17:18, 5 July 2007 (UTC)


 * In the long term, (scale of days to weeks), they adapt as Kainaw mentions. Over the scale of a few hours, a full udder is a discomfort for the animal. Nimur 17:35, 5 July 2007 (UTC)


 * Plus, remember domestic breeds have been selectively bred for generations to produce huge quantities of milk, and to keep producing it. Wild breeds would not have a problem to the same extent as a domestic (dairy) breed. Skittle 21:31, 7 July 2007 (UTC)


 * Domestic dairy cattle are fed and watered in huge quantities; this helps produce vast quantities of milk. Nimur 02:07, 9 July 2007 (UTC)

Hooking up solar panel to appliance
Hi all,

The computer in my apartment is probably the most energy-consuming appliance have. I'd love to be able to hook up a solar panel to it and have it run off of green energy. However, obviously it isn't as simple as that.

I am renting, so have little ability to change the wiring in my apartment or sell back to the grid or anything. And if I just hooked up the panel to my computer, I might get a little power in the day (or I might not, this is Boston), and would certainly get nothing at night.

Is there any system I can use whereby the solar power just suppliments the energy I'm drawing from the grid? Ideally I'd like to be able to instal a solar panel on my roof and attach some kind of large battery (so that it's always charging even when I'm not consuming electricity), and then, when I start consuming electricity, it jumps in and supplies as much electricity it can and lets the grid take up the rest of the slack.

Is there any system remotely like that? And what kind of price would you figure would be on it?

Thanks! --Mike. 17:05, 5 July 2007 (UTC)


 * There are many systems for it, but they are not as "green" as you may like. You need a collector (such as a solar panel and a windmill propped out your window).  You can hook up a stationary bike if you like also.  Anything that produces electricity is fine.  Then, you need an electronic device that uses the electricity collected to charge batteries.  It limits incoming electricity (in case of, say, a lightning strike) and stops charging when the batteries are maxed out.  You obviously need batteries - a lot of them.  That is the least "green" part of the process.  Batteries are rather nasty, but are slowly being replaced with greener ones.  Then, you need a power regulator to manage supplying power from the batteries.  Unless you want to hack your computer, you will be converting the DC in the batteries to AC and then the computer will convert the AC back to DC for you.  A good regulator will let you connect your wall outlet to supplement power when necessary.  Now, that is a lot of electronics you will need.  Electronic production requires a lot of chemicals and power.  So, you are trading the electricity production from the power company for the electronic production of your "green" system. -- Kainaw (what?) 17:24, 5 July 2007 (UTC)


 * As a renter, green energy possibilities are limited. You're not going to get anything really cost-effective in terms of generating your own power as a renter. Your best bet instead is to move towards conservation. Don't leave your computer on at all times, for example. Switch to a laptop model (laptops are designed to be very power efficient). Put as much of your electronics as possible onto power strips and turn off the power strips when they're not in use. Use compact fluorescents in all your light fixtures. When you purchase anything new (say a TV or refrigerator), look for something that's power efficient. Note that a plasma TV will use more power than the same size LCD TV. Incidentally, it's actually your fridge which is the highest power user in your apartment. Finally, if your local power party offers it as an option, sign up for green power. If they don't offer it, pester them about it until they do (or they block your phone number from calling). Donald Hosek 17:47, 5 July 2007 (UTC)


 * I VERY much doubt that your computer is the biggest energy user. Lets examine the facts: According to Energy use in the United States:
 * 32% space heating
 * 13% water heating
 * 12% lighting
 * 11% air conditioning
 * 8% refrigeration
 * 5% electronics
 * 5% wet-clean (mostly clothes dryers)
 * So all of your electronics (including TV, VCR, Satellite, radio, phone, etc) is only 5% of the total - your computer is probably 1% or maybe 2% of your total usage. Your best bet is to turn down the heat/A.C - since heat is eating a third of your budget, saving even 10% of the cost of heating will more than compensate for the PC!  Then you can take shorter showers and fewer baths (and share with a *close* friend!) - turn off lights when you aren't truly, honestly using them and switch to compact florescent bulbs.  If you can do even slightly better at even just one of those things, it'll wipe out the cost of running your PC. Next time you buy a refrigerator/oven/microwave/dishwasher/A.C/water-heater/freezer - look at the energy consumption and cost of ownership numbers. SteveBaker 18:53, 5 July 2007 (UTC)


 * It all depends on individual circumstances -- you can't just take a statistical summary and declare that everyone follows that. For example, that "32% space heating"?  It doesn't apply to me: I've never run the baseboard heaters in my apartment.  Likewise, the A/C only gets a day or two of use each year.  And there's no clothes dryer in my apartment.  I prefer dark environments, so "12% lighting" is a massive over-estimate in my case.  For me, it would look more like:
 * 30% water heating
 * 30% computer (always on, and reasonably busy)
 * 25% refrigeration
 * 10% oven/stove
 * 3% lighting
 * 1% air conditioning
 * 0% space heating
 * --Carnildo 22:52, 5 July 2007 (UTC)


 * I think you are over-estimating your computer(s), as the average computer's power supply is only rated at less than 500W, it usually uses around 200W at full power for a pretty average computer on high load, plus 50W for a 17" LCD monitor that's just 250W for your "average" computer. On the other hand, Water heating, stove/microwave and fridges are count in kilowatts, and although they may not be always on, I doubt they are used less than say 2 hours a day. --antilivedT 00:07, 6 July 2007 (UTC)


 * I agree he's probably overestimating his computer, but you're overestimating everything else! Not everyone uses electric heating (and a good thing, too, as it's horribly inefficient).  If you have natural gas or fuel oil heating, and a gas stove, and a gas water heater, and no air conditioner, your electricity cost for heating/cooling is 0.  And refrigerators are a relatively small load, nothing like a kilowatt.  (Off the top of my head, I think a typical refrigerator draws 4 amps or so, and of course it's not -- or shouldn't be -- on all the time, either.)  So the other big draws are lighting, and major appliances such as dishwashers, microwave ovens, washing machines, and clothes dryers.  (For that last, there's obviously another huge difference in electricity load between the gas and electric models). --Steve Summit (talk) 00:21, 6 July 2007 (UTC)


 * See for some typical consumption figures. Donald Hosek 00:24, 6 July 2007 (UTC)
 * OK - so you're telling us that this 'oksolar' site is reliable? Let's examine what they said.  Firstly, they don't seem to understand the difference between kWatts and kWatt/hours which is a red flag right away for a company that's selling solar panels!! But we'll forgive that.  They claim that your computer uses 240 Watts and consumes 1248kWatt(/hours) in a year.  For that to be true, the computer would have to be pulling 240 Watts 24 hours a day for 216 days out of the year - or 14 hours a day 365 days of the year!!  Who are these online junkies?!  Even if you forget to turn off the PC, when it's idle, the power drops way below 240 Watts when the computer isn't working hard.  Even if you are leaving it on 24/7 to run a website or something, turning off the CRT monitor or letting it powersave properly will get you way below 240 Watts.  240 Watts is when the PC is working hard with graphics and CPU running something really heavy duty - probably with with the hard drive and CD-ROM drive both spinning and the monitor lit up.  Even 500W power supplies don't deliver 500W continually - that's a peak number for when absolutely everything is going at full power at the same time.  The number they give has to be the very most a dedicated net junkie can rack up.  My (really high end) laptop runs from a 24V/4.5A supply - that's AT MOST 108 Watts and typically more like 30 Watts - it runs for maybe 6 hours a day, 356 days of the year.  So the number for me ought to be something like 44kWatt/hrs - not 1248kWatt/hrs.  If they produced such a ridiculous set of numbers for the computers - I don't trust them to get the other things right either.  Last month my apartment used 513kWatt/hrs (air conditioning - Texas!) - of which maybe 3.6kWatt/hrs was my laptop - much less than 1%. SteveBaker 01:37, 6 July 2007 (UTC)


 * I double-checked against last month's electric bill, and if anything, I'm underestimating. Assuming that my computer (actually, one new high-power computer, one very old low-power computer, one router, one cable modem, one KVM switch, and one CRT monitor) draws an average of 250 watts, and is on 24/7/30, then my computer makes for 45% of my monthly electric bill.  My apartment is wired for electric baseboard heating, but I don't use it.  My stove is typically used for 20 minutes every other day (I live alone, so I cook for two days at a time), and the microwave for less than five minutes a day.  Since there's only one of me, and clothes washing is done at a laundromat, I use far less hot water than "average", and I don't have a clothes dryer. --Carnildo 22:49, 6 July 2007 (UTC)
 * Sure - it's possible for the PC to be that big a share of your bill - but you must surely recognise that you are one the very extreme end of the bell-curve here! (I actually don't believe your 45% figure even so - don't you have a refrigerator?  It'll easily out-consume your PC collection.) You have two computers (one old and therefore inefficient), you have lots of peripherals, you have a CRT monitor rather than an energy-efficient LCD - and you don't use electricity for much else.  You obviously live in an extremely mild climate.  But is it reasonable to answer a question like this on the basis of your (extreme!) situation?  It is vastly more likely that our questioner is in the middle of the range of users - for which the number is around 5% for all electrical items (including TV's which are typically a big chunk of it).  Taking an extreme statistical anomaly isn't the way to answer this question in a helpful manner.  For almost everyone, the best policy is to cut down on heating/AC, turn off unneeded lights, switch to compact flourescent lightbulbs, use the microwave more than the stove, set washing machine and dishwasher onto the cooler settings, take showers rather than baths, shower quickly, hand clothes out to dry naturally instead of using a drier, unplug the TV/DVD/Satellite/Cable-box when it's not in use ("Turninng it off" probably doesn't really turn it off), turn off your PC when not in use (or at the very least, turn on all of the power saving settings and turn off the monitor whenever you walk away from the keyboard for a few minutes or more.  Unless you are a VERY anomalous electricity consumer or already very diligent about these things - then doing any ONE of those things will save more electricity than it takes to run your computer. SteveBaker 20:36, 7 July 2007 (UTC)
 * Although not effective use of money, solar panels could be carefully connected into the power supply of the computer, somewhere where there is DC; probably close to large capacitators. This would reduce the computers usage of mains power a little bit.  Easy to burn out things though. Could be dangerous. Polypipe Wrangler 00:52, 6 July 2007 (UTC)


 * This is dumb - this is INSANELY DUMB advice. It's a stupid thing to do your PC.  Of all of the appliances in your home - the PC is by FAR the most vulnerable to power supply glitches.  If you have solar cells - connect them up to your refrigerator, use it to charge a 12v battery and use an inverter to drive a table lamp or your TV - it doesn't give a damn if the sun goes behind a cloud or a pidgeon lands on the panel and casts a shadow over the cells.  Truly - it is not thinking at all logically to pick the PC as the thing to improve.  Literally every other thing you own that consumes electricity can be addressed as a source of power savings that will be easier and more effective than messing around with what is probably the most expensive, delicate and precise appliance you own!  WHAT ARE YOU THINKING?!?!?!? SteveBaker 01:37, 6 July 2007 (UTC)


 * There's nothing to do but second this. Trying to use a solar panel in an apartment, and especially to power your computer, will probably cost you more than it saves, especially when your PC blows up --ʇuǝɯɯoɔɐqǝɟ 02:00, 6 July 2007 (UTC)
 * Modern computers are actually quite robust when it comes to power. As long as your solar panels are supplying enough power to keep the computer running, or you've got a battery to take up the slack, there's nothing wrong with hooking your computer up to them.  A light bulb is about the worst possible thing you can hook up to a solar panel: since you usually don't need artificial light during the day, you must have a battery to store the power, and batteries use an incredible mix of toxic chemicals. --Carnildo 22:53, 6 July 2007 (UTC)

Ok, if you're doing this for environmental reasons, check out http://terrapass.com/ - it will help far more than a solar panel ever will. If you're doing it for cost reasons... it would be best to just buy cheaper appliances. The 200$ maximum your PC might possible cause you in costs if you run it constantly is not worth any solar panel powerful enough to offset it. --ʇuǝɯɯoɔɐqǝɟ 02:05, 6 July 2007 (UTC)

Klinefelter's syndrome and homosexuality
Is there any links between Klinefelter's syndrome and homosexuality? Are there any scientific proof that Klinefelter's syndrome may cause homosexuality? Has there ever been any (non-scientific) speculation about the possible connections? ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 17:33, 5 July 2007 (UTC)


 * A cursory examination of the relevant literature indexed by PubMed reveals very little work that looks at homosexuality in the context of Klinefelter's. Ratcliffe S. (1999) "Long-term outcome in children of sex chromosome abnormalities"  Arch. Dis. Child. 80(2):192-5 failed to identify a link, though the study was relatively small (19 XXY boys, none of whom demonstrated homosexual tendencies).
 * Worth bearing in mind is that the incidence of Klinefelter's is about 1 in every 700 men, whereas the fraction of the male population that is homosexual is on the order of 1 in 10&mdash;so even if all Klinefelter's individuals were homosexual, it would make a relatively small contribution to the total number of homosexual individuals. TenOfAllTrades(talk) 19:04, 5 July 2007 (UTC)
 * Oh ok, I see. Thanks for the info! ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 22:37, 5 July 2007 (UTC)
 * Where does that one in ten figure come from, I hear it a lot, but in my personal experience (I know, not statistically significant) I wouldn't think it was even close. Are there really 6 million homosexuals in the UK? Cyta 07:00, 6 July 2007 (UTC)
 * I don't have a source to hand, Cyta, but expect I can find one soon with some digging. I used to be on the Equalities group of a community regeneration company, and that is the figure we worked with. One thing to remember is that you almost certainly know many more gay people than you think you do - it's just that some will not be "out" at all, others will only be out with certain people or in certain circumstances. DuncanHill 09:28, 6 July 2007 (UTC)
 * I think the actual number is about 3% from the last peer reviewed study I've seen with some varations in rural and urban settings. --Tbeatty 17:26, 7 July 2007 (UTC)


 * I read somewhere that no-one is completely defined as homosexual ro heterosexual or whatever. They said that some people are only more straight or gay than others. I guess that there are fewer more-gay people than there are bisexuals and straight people. ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 09:18, 6 July 2007 (UTC)
 * The article Kinsey scale is relevant to the theory of a continuum of human sexual orientation. DuncanHill 09:21, 6 July 2007 (UTC)
 * Obviously in order to quote the '1 in 10' concept we would have to get our terms better defined. As others have mentioned the term 'homosexual' leaves the field rather open to include people that may define themselves as straight/heterosexual in society but are nonetheless somewhat homosexual. Even the word 'homosexual' can mean anything from a) a person that identifies themselves as homosexual, to b) a person that is attracted to the same sex, to c) a person that engages in sexual activity with members of the same sex but not necessarily exclusively (e.g. bisexuals, curious, etc), to d) people that exclusively or predoiminantly engage in sexual activities with only members of the same sex, etc. Indeed a rainbow. My point is, that I don't agree with the "1 in 10" statement at face value. I don't believe that 1 in 10 people are predominantly gay. I would accept the 3% rule, however. But if you change it around to include c) a person that engages in sexual activity with members of the same sex but not necessarily exclusively, then maybe it's more accurate. Rfwoolf 12:29, 8 July 2007 (UTC)

The UK government puts the figure at 6% (they wanted to asses the "cost" of civil partnerhip as couples pay less tax) but they didnt do any original research, they just collated all the previous studies. Helpfully, they refuse to add the question in the census. Also, hasn't Kinsey been wildly discredited? I could perhaps accept that 10% of men have "done stuff" with other men but cleary the 10% gay figure is way off the mark. I like 5% - one in twenty. a nice round number...130.88.205.43 11:10, 11 July 2007 (UTC)

An unusual application of tack adhesive
Would it be even theoretically possible to use tack adhesive to hold a shelving unit full of books to a wall? Neon Merlin  18:17, 5 July 2007 (UTC)


 * Theoretically - yes - practically - no! Well, there are two issues here:
 * What area of shelf is in contact with the wall via the adhesive? Every square inch of tack will require a certain amount of force to pull it off the wall - the more square inches there are, the more force it'll take - so the more weight it can support.  If the area is large enough - it should hold.  So your best chance is to fix (using nice strong screws/nails) a large 'back board' to the back of the shelf - then cover that with tack adhesive.
 * Shear forces. The weight of the shelf+books (which are insanely heavy BTW!) is acting downwards, parallel to the wall - but the tack adhesive is also resisting pulling forces at 90 degrees to the wall. The complicating factor is that if it more or less resists the shearing force, the front edge of the shelf is trying to move down - while the back of the shelf is staying stuck.  That's causing a rotation - so what's going to happen is that the tack behind the bottom of the shelf will be squashed while the tack at the top of the shelf is being pulled - the tack that's being squashed is doing some work in resisting the shear forces - but the tack at the top of the shelf is being pulled off the wall at more or less 90 degrees...AND resisting the shear forces.  This suggests that you want to have more area of tack above the shelf than below it in order to better resist that force.
 * But no - it's bloody obvious that it's going to fall down! Duh! SteveBaker 18:37, 5 July 2007 (UTC)


 * If you're in an earthquake zone (like me!) you might want a sturdier shelf than that. I recall a statistic (probably from this book) that most earthquake injuries are due to falling books and bookshelves, and falling glass from lights and windows.  (Specifically, they cite "For example, in the 1994 magnitude 6.7 Northridge earthquake, 55% of quake-related injuries were caused by falling objects, such as televisions, pictures and mirrors, and heavy light fixtures." Nimur 21:24, 5 July 2007 (UTC)


 * Excuse a poor Englishman... what is tack adhesive? DuncanHill 22:39, 5 July 2007 (UTC)


 * Blu Tack. Also, you should consider that if the wall is painted, it's not the wall that will be holding up the shelf, but the paint. Paint has a nasty habit of peeling right off if you pull too hard. —Bkell (talk) 22:47, 5 July 2007 (UTC)
 * That's not a problem so long as the adhesion between paint and wall is better than between paint and tack adhesive. So that if something is going to give, it'll be the adhesive, not the paint! It is an important property of Blu Tack that it does NOT pull paint off the walls - it's the single property that it has that makes people use it!  So unless the walls are in terrible shape (such that even tacking up a poster with blu-tack would pull off the paint), it doesn't matter how much weight you try to hang off of it - the tack will give up before the paint does. SteveBaker 13:32, 6 July 2007 (UTC)
 * That's a good point. —Bkell (talk) 00:32, 11 July 2007 (UTC)

Burning wood = carbon neutral??
On the Terrapass.com site there is a list of FAQs about energy consumption. Link (though it's a php page, so not certain if you'll see the FAQs without further navigation). The last FAQ is this:

= What about my wood stove? = Technically, the burning of wood is carbon neutral. Of course there are many other downsides to it, and we're not recommending it as a substitute for gas or other more traditional energy sources.

Really? I had understood that combustion of wood releases all the carbon that was stored in the wood out as carbon dioxide into the air. Is that not correct? The wood and combustion articles don't help much, except that I see that CO2 is indeed often on the right side of the chemical equation.

Maybe by "technically carbon neutral" they mean that no new CO2 got created, because it was in the air before the tree consumed it? If so it seems that the wording is a little silly -- after all, the carbon in fossil fuels may well have been CO2 before it went into the fossils...

Thanks! Mike. 18:53, 5 July 2007 (UTC)


 * The idea is that if you want to use wood as a fuel, you're going to have to keep growing new trees. Burning any plant that you've grown from scratch is carbon neutral, in that you pulled all the carbon in the plant out of the air in the first place.  The key difference between burning wood and burning oil is that we actually can grow new trees (on a non-geological timescale). TenOfAllTrades(talk) 19:27, 5 July 2007 (UTC)
 * Do all of the carbon in the wood go into the air though? Because, what is that black stuff (ash) that remains after you burn wood? Isn't that like the left-over carbon? ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 22:41, 5 July 2007 (UTC)


 * If the fire is properly oxygenated, and you let it burn to completion, the stuff left has almost no carbon content. --Carnildo 22:56, 5 July 2007 (UTC)


 * So long as there is no deforestation being caused by people cutting down trees for firewood - then we're carbon-neutral. The important thing is that new trees are being planted and looked after until maturity.  If this really bothers you - dig a deep hole in your back yard - every time you burn a log - toss another one into the hole and bury it.  That way you're not only carbon neutral - you're actually 'sequestering' carbon. SteveBaker 01:03, 6 July 2007 (UTC)

I hope it's carbon neutral. That means burning oil is carbon neutral, since it came from plant matter. Points out the silliness of "carbon neutral" though. --Tbeatty 17:22, 7 July 2007 (UTC)


 * I thought oil was algae and zooplankton, not plants? It's coal that's plants. Anyway, burning fossil fuels would be carbon neutral if you burnt them at the same rate as, or slower than, the rate they are being made at. Skittle 21:25, 7 July 2007 (UTC)
 * surely if you're burning wood slower than you're growing it it can't be carbon NEUTRAL, which would suggest no loss or gain of CO2. :-P Aamackie 06:07, 9 July 2007 (UTC)

I thought of this a few days ago but forgot to post it. Note that properly calculating carbon neutrality is not a simple matter and it's safe to say that in the current enviroment, you won't be carbon neutral by simply replacing all wood that is burnt. Producing and processing said wood from the seed to your final product almost definitely requires input of additional energy in the form of petrol/diesel (vehicles, chainsaws etc) and electricity (saw mill, perhaps irrigation systems, etc) and likely also in other means (fertilisers, pesticides). There's also the human labour to consider. I don't actually agree with tbeatty here, it is IMHO a useful concept but it needs to be properly considered to have any use Nil Einne 19:24, 15 July 2007 (UTC)

Terminal shoot - English botanic name?
Hello, please does anyone know the term of "Terminaltrieb" (German) in English, it is the main shoot of a tree and determinates the direction of its growth (in contrary to the offshoots). Many thanks in advance, --birdy (:> )= 20:44, 5 July 2007 (UTC)
 * You have it perfectly in the title of your question, unless I have misunderstood you. The english term is indeed 'terminal shoot'. Lanfear&#39;s Bane

Try Apical Shoot. Hardyplants 00:02, 6 July 2007 (UTC)


 * Thanks a lot! So terminal shoot and apical shoot are synonyms? --birdy (:> )= 12:03, 6 July 2007 (UTC)


 * I'm not sure about horticulture but in botany you're probably looking for either the apical meristem (most likely) or the shoot apex which is properly the shoot apical meristem plus the leaf primordia. KP Botany 04:00, 7 July 2007 (UTC)

dimmer switch efficiency
I want to buy a dimmer switch for an incandescent, not cfl, bulb. I understand that modern dimmers are more efficient than old variable resistor style. My question is: Are some brands or models of dimmer more energy efficient than others? I notice that one manufacturer markets what looks like the same switch at the same price with two different styles of packaging, one of which says it is 1/4 more efficient (but does not specify what this means).


 * Modern dimmer switches work because they are powered off an AC circuit; as a result, they can take advantage of the fact that the voltage varies by only allowing a current to pass when the voltage is high enough; as a result, they waste less energy as heat than an old-fashioned resistors (no energy is needed by circuit that doesn't flow). Presumably the more efficient one is of a lower resistance (as dimmers no longer rely on internal resistance to work); check whether the back of the box gives either resistance or heat output (both would be good indicators of efficency). Laïka  23:17, 5 July 2007 (UTC)


 * Don't they use PWM so there isn't much variation on structrually similar units. --antilivedT 23:25, 5 July 2007 (UTC)


 * You could call what a dimmer does PWM, though it's sort of a poor-man's simulation; I've usually heard it called "chopping". But it does still have the property that the dimmer is always either "on" or "off", and hence (theoretically) there's no loss, and the process is perfectly efficient.
 * If there are efficiency variations between models, they're bound to be slight.
 * What people here are calling "old-fashioned", resistive dimmers are more than just old-fashioned, they're positively obsolete. I've never seen one, and I doubt anyone reading this (at least, if they're in the U.S.) has, either.  As far as I know, all dimmers have been choppers, for decades now. --Steve Summit (talk) 00:13, 6 July 2007 (UTC)
 * My college still had one in one of it's original buildings. It had this monstrous heat sink attached to it.  It just looked like such an obviously bad idea.  &mdash; Laura Scudder &#9742; 01:11, 6 July 2007 (UTC)
 * I think the correct term for the circuitry in a dimmer switch is triac, which is similar to PWM in concept, but not in implementation. The article elaborates on the details.  Nimur 04:42, 6 July 2007 (UTC)
 * "Triac" is the name of the principal component in those dimmers. You can (and many people do) call it "a triac circuit", but that's an imprecise term, as there are of course other circuits that also use triacs.  (That is, saying that "the" name for the circuitry in a dimmer is "Triac" is like saying that the name for the circuit inside a radio is "transistor", or that the name for the circuit inside a computer is "microprocessor".) —Steve Summit (talk) 05:08, 6 July 2007 (UTC)
 * I have definitely seen resistive dimmers. At a motion picture theater built in the 1920's which had been a vaudeville palace in bygone years, the dimmer system had a bank of resistive dimmers, which could be gang-operated by a motor. The resistance element could have been nichrome wire, but in earlier years it could have been iron wire. It could be set up to dim individual lights or groups of lights, much like present-day theatrical lighting systems. Edison 04:16, 7 July 2007 (UTC)

To answer the original question, all phase control dimmers are very efficient. The triac (the power switching element) drops less than a volt when switched "on" and dissipates no power when switched off, so even on a 120 volt circuit, less than 1% of the voltage is dropped in the switch; on a 230 volt circuit, less than 0.5% of the voltage is lost in the power switch. Because of this, I think we can safely call the efficiency of the dimmer >99%. Even a perfect dimmer would only improve that efficiency by 1% (120 vac) or 0.5% (230 vac).

The big improvement that's coming is sine wave dimming instead of phase-control dimming. By replacing the slow triacs with high-speed power MOSFETs, the dimmers will be able to preserve the sine wave shape of the power voltage. This, in turn, will eliminate the problem of lamps "singing" and fan motors "buzzing" when dimmed down.

Atlant 13:48, 8 July 2007 (UTC)


 * It would seem to me a big problem is that most dimmers would still not work with CCFLs, at least as long as traditional light fixtures and wiring is maintained. Given the inefficiency of incandescent bulbs, while it's good that the dimmers are efficient in the end you're still running an incredibly inefficient system. LEDs are AFAIK easier to dim then CCFLs so perhaps that will help although I'm not sure if traditional fixtures and wiring will work. Edit: I see this is covered somewhat in compact fluorescent lamp Nil Einne 12:50, 16 July 2007 (UTC)

hi, my guestion is about c++
hi, i have some guestions about c++ programing language they are very important for me i didn't find the answer for these guestions ,, i will be delighted if someone help me in this field (c++) and answer my questions first which is difficult for me to know how to make it in matrix - i want to make the size of the array is variable, which is entered by the user or the size depends on variables. or there is no way to make the size of the array variable ,,,it should be the size constant(value).

i.e :

please help me in this matter, it means a lot to me .....


 * Go to the computing reference desk --ʇuǝɯɯoɔɐqǝɟ 23:31, 5 July 2007 (UTC)
 * Future computing questions are best asked at the computing desk. In this case, you should read about malloc.  Wikipedia is an encyclopedia, not a tutorial service; you might be interested in the C++ wikibook. Nimur 00:37, 6 July 2007 (UTC)
 * Almost. C++ typically uses (well emphasizes) new and delete instead of malloc/free, although the latter are still available. Look at dynamic memory allocation in any beginning C++ book. But yes, the Computing Desk will probably be more open to these sorts of questions. --Bennybp 00:45, 6 July 2007 (UTC)
 * Just replace 'int a[b];' with 'int *a = new int[b];' - when you are finished with the array, run 'delete [] a;' SteveBaker 00:57, 6 July 2007 (UTC)
 * Also the C++ Standard Template Library (STL) has lots of useful containers, for example in this case a std::vector which have variable size. is a good guide. Not sure if it's possible to set an upper size limit, so it may not be what you want now, but these containers are useful and have a series of preprogrammed functions (such as .size which tells you the size of the vector) which can come in handy. Cyta 07:07, 6 July 2007 (UTC)