Wikipedia:Reference desk/Archives/Science/2010 December 17

= December 17 =

Pterodactyls
Could someone explain for me in layman's terms, what the difference between a pterodactyl, pteranodon and a psterosaur is? I've seen all three terms used interchangably in writing in the past. Thanks. —Preceding unsigned comment added by 95.148.109.104 (talk) 00:09, 17 December 2010 (UTC)
 * Pterosaurs were the whole order of flying reptiles. Pterodactyloidea was a suborder of pterosaurs. Pteranodon was a genus of large flying reptiles. --  T H F S W  (T · C · E) 00:29, 17 December 2010 (UTC)
 * And I really wanted to answer that question! :) But yeah, he covered it. Crimsonraptor (talk) 00:37, 17 December 2010 (UTC)


 * In even more layman's terms... Pterosaurs is a term which includes a lot of different species of dinosaurs. Pteranodon is a sub-group of species within that group. Pteranodon is a sub-group within that group, which contains two species, which are usually the specific birds you think of when you refer to Pteranodons. --Mr.98 (talk) 14:38, 17 December 2010 (UTC)
 * "Birds", maybe, but not birds! --Sean 17:24, 17 December 2010 (UTC)
 * That's not layman's terms, it's just completely incorrect. THFSW had it right - none of the terms listed have ANYTHING to do with dinosaurs or birds. Please be more careful before you try correcting someone who knows what they're talking about. 64.235.97.146 (talk) 18:11, 17 December 2010 (UTC)

Untreated ringworm does... what?
Ringworm is apparently quite common in both humans and other animals. When humans get it (assuming a certain level of medical care is available) they can resolve the problem quite quickly with modern antifungals and such. But what happens if the dermatophytosis is left untreated, as one would expect for a stray dog or cat? Does the fungus just happily reside on the surface of the skin indefinitely? Does it eat deeper and deeper into the tissues? The ringworm article kind of sucks. The Masked Booby (talk) 01:35, 17 December 2010 (UTC)
 * I would imagine that ringworm may itself not be harmful in the long term, but it greatly increases the risk of secondary infections, due mostly to the fact that you are scratching it all the time. Those secondary infections could be a major problem, and could perhaps be too numerous and varied to list here.  -- Jayron  32  02:25, 17 December 2010 (UTC)
 * There's an old story that claims that a ringworm around the abdomen will kill you when it completes a full circle. Not sure of that statement's validity. ~ A H  1 (TCU) 02:28, 18 December 2010 (UTC)
 * The same myth exists with shingles. Complete balderdash of course! Caesar&#39;s Daddy (talk) 08:25, 18 December 2010 (UTC)


 * Side Issue: Does the ban on medical advice extend to veterinary medicine? Sfan00 IMG (talk) 12:01, 20 December 2010 (UTC)

Tiger cheese
Are there any carnivores whose milk is consumed by humans? L ANTZY T ALK 03:36, 17 December 2010 (UTC)


 * Historically and prehistorically, it seems rather unlikely. You'd have to feed them meat edible to humans, whereas cows and such eat things we can't. Plus they'd be liable to be a whole lot less docile and prone to evil thoughts of eating their keepers. But hey, you may have hit upon a novelty product. Clarityfiend (talk) 04:55, 17 December 2010 (UTC)


 * But lots of carnivores eat things we wouldn't want to eat, like cats eating mice and dogs eating skunks (which might just curdle their milk :-) ). StuRat (talk) 05:02, 17 December 2010 (UTC)
 * Ugh! Finish all yummy mice, Tumak. Are Neanderthals in cave somewhere starving! Clarityfiend (talk) 05:24, 17 December 2010 (UTC)


 * People do drink dogs milk sometimes, here's a vid of a kid, but adults probably do it too (although maybe not directly). There is also pig cheese and presumably milk too. Ariel. (talk) 06:25, 17 December 2010 (UTC)


 * (Edit Conflict) Romulus and Remus legendarily fed on a wolf's milk, and I vaguely recall accounts (not necessarily verified) of more recent feral children similarly surviving temporarily on an adoptive canid or other wild animal's milk. 87.81.230.195 (talk) 06:37, 17 December 2010 (UTC)


 * Didn't the King James Bible have a verse in Genesis saying something like "Seven sons did milk a bear?" Edison (talk) 00:59, 18 December 2010 (UTC)
 * If you're going to call a bear a carnivore (hint, they're not, except Polar bears), then we should also consider Human milk, which many people consume as an infant, and occasionally later in life. Buddy431 (talk) 02:48, 18 December 2010 (UTC)


 * A couple more thoughts. The cost of keeping meat-eating critters is much higher than what you could possibly get back in the form of milk. On a more practical note, who're you going to get to milk a tiger? Clarityfiend (talk) 02:53, 18 December 2010 (UTC)


 * Is this whole thread somehow inspired by Tiger's Milk? --Trovatore (talk) 03:19, 18 December 2010 (UTC)

Crazy kid again... with more subjective thoughts that y'all will hopefully objectify
So through a little bit of work with a pencil and a sheet of paper, i wrote out an arbitrary word problem requiring simple algebra to solve. It was then I realized that if i were to translate this word problem into an equation that each kind of word in the english language (i.e. noun, verb, adjective etc.) would have a parallel mathematical meaning. In algebra class in middle school I was told that the word "of" just meant times. and that makes perfect sense. If was wondering... If I was to ask myself simply "What do I see in my room?" could I answer it in an equation form like ... I see a blanket then assign a variable to the blanket lts say (B) and a mattress then label that mattress L.. to answer my question I would now be able to say What I see = B + M... what I am curious about is going further. Let say I wanted to describe M in more detail by maybe.. saying that whatever function (mattress manufacturing and shipping and whatever else it took to get to my room) lead to the mattress being in my room and being part of my answer for what I see in my room...how would I combine certain aspects of my overall equation

Given

What I see in my room = B + M

M exists because of the function of why it's in my room M(x), x being whatever variables account for why the mattress is in my room.

So now I have

What I see in my room = B + M= B + M(x)

Is any of this correct at all?

Where can I find instructions on how to translate words into pure equations? — Preceding unsigned comment added by BloodWasPassion (talk • contribs) 04:39, 17 December 2010 (UTC)
 * What you're trying to do looks like the branch of artificial intelligence called knowledge representation and reasoning, which typically represents real-world information in semantic networks. It also touches on computational linguistics, in particular computational semantics.  And all of this is a part of natural language processing.  Red Act (talk) 05:15, 17 December 2010 (UTC)

How did the mattress get from L to M? You might enjoy Word problem (mathematics education) or Internet Relay Chat (e.g. ) more than the reference desk. Ginger Conspiracy (talk) 05:34, 17 December 2010 (UTC)

About Styrofan (construction Chemical from BASF )
Hi, This is Vinay from Bangalore India. can some one give me answers to the following: a) What are the chemical compositions of Styrofan b)Why & how Styrofan should be used in READY MIX CONCRETE what are the proportion c)How many types of styrofan is there & how many of them are for ready mix concrete PLZ SOMEBODY HELP ME ITS VERY URGENT TRIED LOOKING THE WHOLE INTERNET BUT COULD NOT FIND MUCH PLZ PLZ IF IT IS POSSIBLE TO MAIL THE ANS here is my id [removed] . looking forward for the ans

with regards Vinay —Preceding unsigned comment added by 59.97.26.3 (talk) 09:59, 17 December 2010 (UTC)


 * A) It's water-based styrene butadiene
 * B) It's a protective coating or binder used for fibre bonding or as an adhesive.
 * C) There seem to be 19 types

Zzubnik (talk) 10:15, 17 December 2010 (UTC)


 * I removed the poster's email address, per refdesk standard (ask-here, answer-here; avoid spam-harvesters, etc.) DMacks (talk) 10:22, 17 December 2010 (UTC)

This appears to be the internet resource you're looking for... Physchim62 (talk) 11:06, 17 December 2010 (UTC)

Maxwell's demon (MADE IN JAPAN)

 * http://neocoat.jp/neo/english/comparison.html

It seems like this revolutionary paint does not decompose under the sun (chemical heat absorption). Its high-tech molecules just vibrate and keep heat from entering your house.

Are they selling Maxwell's demon by the bucket in Japan? -- Toytoy (talk) 10:42, 17 December 2010 (UTC)


 * This is the sort of question where things can get very complicated. So, forget about this paint advert which attempts to baffle with science and read this simplified explanation of reflectance/ low emissivity. Low emissivity for use at high  temperatures Wikipedia does have an article about  low emissivity but it is not easy to take in at a single reading.  Note also that high performance heat sinks, such as those found in top class sound systems and  on radioisotope thermoelectric generators etc., are nearly always matt black.--Aspro (talk) 14:58, 17 December 2010 (UTC)


 * Maybe the best WP article is Radiant barrier--Aspro (talk) 15:31, 17 December 2010 (UTC)

I think there shall be a way to make a not-so-Maxwellian-demon heat shield:


 * You have to have a material that is capable of phase or chemical change at about 25 deg C.
 * The location must have very hot days (e.g., 35 deg C) and very cold nights (e.g., 15 deg C).
 * The target room temperature is about 25 deg C.
 * You have a great scientist to make this material a commercially successful paint.

During the day, the material absorbs solar energy and undergoes phase or chemical change. The change keeps the external surface from getting very hot. As a result, the house does not get too hot during the day. The paint layer has to be very very thick to act as a heat sink.

Then during the night, the external temperature drops very quickly. The paint releases heat and its phase or chemical change is reversed. Since the inside of the house is warmer than outdoors, the paint releases most of its heat to the cold outside air.

During winter days, this dark-colored material absorbs heat and heats up your home.

Then the paint releases heat to the outside during winter nights. You must have a good heater and a cheap source of fuel otherwise you will be very sorry ...

This certainly is not a solution for everyone of us. -- Toytoy (talk) 16:36, 17 December 2010 (UTC)


 * That has nothing to do with the paint, which was the subject of your question. Your prediction is now too far into the realms of a crystal ball to warrant further discussion. You have now shown you are just asking lots of questions here on the reference desks because you have nothing better to do. --Aspro (talk) 18:43, 17 December 2010 (UTC)
 * Is that not allowed? 81.131.62.210 (talk) 19:21, 17 December 2010 (UTC)
 * ??? It's not a crystal ball to ask if something is scientifically feasible. He's not asking about the future. If you don't have anything to say about it... then just don't say anything! Don't be so arrogant as to proclaim that nobody can have anything to say about it. --Mr.98 (talk) 13:24, 18 December 2010 (UTC)

Cryogenic revitalization
Is it possible to revive someone many many years into the future after they have been cryogenically frozen?


 * We do not presently have the ability to do this, and it is unknown if we will ever be able to do that. Some people do freeze themselves (typically shortly after death), with the hope that future doctors will one day learn how to revive frozen people.  See: Cryonics.  Dragons flight (talk) 18:12, 17 December 2010 (UTC)


 * Also note that the freezing process causes ice crystals to grow inside the cells, which destroys them. Unless they find a way to completely prevent this, the chances of ever reviving someone so damaged are very low. StuRat (talk) 19:04, 17 December 2010 (UTC)


 * There are a few types of animals that are capable of freezing and then reviving -- their cells make a sort of antifreeze that prevents the formation of ice crystals. My sense is that if animals can do it, then sooner or later there will be a technology that allows it to be done to humans, but of course we're in the crystal-ball realm here. Looie496 (talk) 20:34, 17 December 2010 (UTC)


 * Freezer burn is a major problem in this process, and surgeon nanorobots could be one solution. ~ A H  1 (TCU) 02:22, 18 December 2010 (UTC)


 * Vitrification freezers are another. It's a freezer and a microwave; two appliances in one! The Japanese have the best, in the food processing (edamame/soybean preservation) industry, since ice crystals change the texture of frozen vegetables, too, by destroying cell walls. Ginger Conspiracy (talk) 13:44, 18 December 2010 (UTC)


 * I've always thought one of the biggest problem with cryogenics is that you'll be trying to revive someone who is not only frozen but who is already dead. We need to find a cure for death before we need to worry about defrosting. DuncanHill (talk) 13:48, 18 December 2010 (UTC)


 * Reviving a mammal who died because of hypothermia and has been preserved since (i.e. by cold) is possible. It takes an electric shock such as from a defibrillator, an artificial respirator, and a way to evenly warm them back up. If there has been severe ice damage, they won't revive. With moderate ice damage they will revive and die a horrible, really disgusting and painful death in less than a day. Light ice damage is survivable with a decreased expected lifespan and infertility in females (the ova are the largest cells, and thus most susceptible to ice crystal damage.) There seems to be a general agreement among researchers to discontinue cryonics research on mammals over a kilogram until vitrification technology improves such that ice crystals aren't expected to be a serious issue.  Improvements have been slow and steady, but vitrification freezers are nowhere near human mass range yet. Ginger Conspiracy (talk) 08:14, 19 December 2010 (UTC)

RationalWiki's Cryonics article is much better than ours. Ginger Conspiracy (talk) 01:58, 19 December 2010 (UTC)


 * It's generally believed that their memories and personality are stored in the structure of the brain, so it's not theoretically impossible. Whether or not our current cryonics technology is sufficent and whether or not technology will be sufficient to repair the damage or replace it outright are open questions. There's not much we can do to find out if it's possible. We may be able to work out how much damage is being done to the neurons, and find out if it's too much for the person to live normally, but there's no reason to believe most of that damage couldn't be fixed. There's a big difference between a neuron being gone, and being replaced by one with a best guess of where it's supposed to attach. Theoretically, they only need enough information to be able to distinguish you from the average person. They don't need your body to find out how humans in general work. — DanielLC 19:29, 20 December 2010 (UTC)


 * There is no reason to believe that long term survivability is not directly proportional to the mass of body tissue which can be frozen and thawed without ice crystals, which is a physics appliance engineering optimization problem. I am confident that the colonization ships are on schedule. Ginger Conspiracy (talk) 20:46, 20 December 2010 (UTC)

Error in Image
In the image File:Decay chain(4n+1,Neptunium series).PNG it says Uranium-223 inside the octagon it should say Uranium-233. 174.112.211.143 (talk) 21:01, 17 December 2010 (UTC)
 * Fixed it, thanks. --Sean 21:26, 17 December 2010 (UTC)

What percentage of the air expelled rearward from a jet engine actually thrusts an aircraft forward?
Seems like a pretty basic question, which would have the pretty basic answer of "all of it". But I've been looking around our articles and widely through google and can't seem to get the answer. What I am trying to determine is how much of the thrust comes from the exhaust from the jet engine pushing against the atmosphere behind the aircraft, and how much comes from the thrust pushing forward against the engine itself. How is it that in a vacuum a rocket/jet engine pushes itself forward even tho there is nothing behind it to push on? Anyone? —Preceding unsigned comment added by 222.152.15.198 (talk) 21:29, 17 December 2010 (UTC)
 * You don't need the mass you expel out the rear of the rocket to "push" against anything. The mere fact that you are expelling that mass is what propels you.  Googlemeister (talk) 21:35, 17 December 2010 (UTC)
 * Do you mean that the mass is pushing against the engine to make it (and the aircraft) go forward? I'm not trying to be cute here Googlemeister. If I blow up a kid's balloon and then let it go it will fly around like crazy. Will it behave the exactly same in a vacuum as in my house?  If yes, then I guess the answer to my question is that zero % of the air expelled rearward from a jet engine actually thrusts an aircraft forward. —Preceding unsigned comment added by  222.152.15.198 (talk) 22:30, 17 December 2010
 * Yes, it will behave much the same in a vacuum. That means 100% of the gas expelled from a rocket pushes it forward, but it's all done by Newtonian reaction, not by pushing against some external medium. You get the same effect by firing a gun (the reaction pushes you backward) or a firehose. The little maneuvering jets that astronauts use to fly around when they're outside a space station are quite like a can of hairspray, and indeed an astronaut could take a (big) can of hairspray with them and use it to move them - they just point it in the opposite direction to where they want to go and push the button. -- Finlay McWalter ☻ Talk 23:08, 17 December 2010 (UTC)
 * Let's say you're kneeling on a skateboard and you're holding a brick. You throw it forwards as hard as you can.  What happens to you?  You go in the opposite direction, and it's not because the brick is pushing against the air.  See Newton's Third Law. --Sean 22:13, 17 December 2010 (UTC)--Sean 22:13, 17 December 2010 (UTC)
 * I think the answer to this question might not be simply 100% or 0%. Let's compare walking, flying in a jet, and flying in a rocket. In all three cases, some fuel is consumed, to get the energy to move something, to obtain an reaction in the opposite direction. In the case of walking, we burn food and move the earth very slightly. The jet burns fuel and moves the air. The rocket burns fuel and moves the fuel. Question is, can't the jet also be said to be expelling its fuel to some extent? It needs air in order to burn the fuel, but if the air was carried onboard, it would be a rocket, and its fuel would be part of what it was expelling. So, now I'm just confused by what the question means, sorry. 81.131.15.161 (talk) 06:49, 18 December 2010 (UTC)
 * Ahhhhh, wonderful wikipedia. Thanks for your input, but I'm sorry my clumsy question wasn't clear. What I was trying to find is whether the stuff coming out of the back of a jet engine propels the aircraft forward by pushing against the air behind it or does it propel the aircraft forward by by pushing against the engine? Finlay McWalter has cleared this up admirably, but I can tell you that reading wiki's relevant articles does not truly spell out the answer for people not au fait with the science terminology.  Like me.  —Preceding unsigned comment added by 222.152.15.198 (talk) 07:10, 18 December 2010 (UTC)
 * And Finlay explained that it is not by anything "pushing against" anything. I'm guessing you're thinking of newtonian reaction as a sort of 'pushing against', but I don't think that's very helpful: in Sean's example, is the brick pushing against you? --ColinFine (talk) 00:14, 20 December 2010 (UTC)
 * I don't see why you don't think it's helpful. The answer is, yes, the jet engine is pushing against the exhaust, and the exhaust is pushing back.  The original question seems to ask for a breakdown of how much of the thrust comes from each; that part is based on a misunderstanding.  The answer is that the engine pushing on the exhaust, and the exhaust pushing back, are actually the same phenomenon.
 * So 100% of the thrust comes from the engine pushing on the exhaust, and also 100% comes from the exhaust pushing back. And that doesn't make 200%; it's just two ways of saying the same thing. --Trovatore (talk) 00:19, 20 December 2010 (UTC)
 * Huh! I thought I had it sorted and then, whammy! Surely that would create zero effect? The engine pushes aft at X and the exhaust pushes forward with the same X force?  —Preceding unsigned comment added by 222.152.15.198 (talk) 00:32, 20 December 2010 (UTC)
 * Get a sack of bricks. Hold them while standing on a skateboard. Throw the bricks very fast one by one behind you. Use this analogy to answer all your questions. 92.24.188.27 (talk) 16:02, 21 December 2010 (UTC)
 * Sure, but you didn't explain why! If I let my balloon go in a vacuum it will fly around madly. Doesn't that mean that 100 % of the pressurised air released from the balloon drives it forward by pressing against the inside of the balloon, and zero % of the expelling air drives the balloon forward by pressing on something outside the balloon (because there is nothing to act against)? Ah, the answer was there all the time, in Finlay McWalter's post above. As you were.
 * Here's the famous 1920 New York Times editorial that says rockets can't fly in space. 81.131.15.161 (talk) 08:29, 18 December 2010 (UTC)
 * But let's be fair. They did apologize for that... during Project Apollo.  --Anonymous, 18:00 UTC, December 18, 2010.

Does gravity slow down time?
Someone said that clocks are faster in space than they are here on Earth. Supposedly standing next to a pyramid will slow down time by a fraction of a second. Is this true? ScienceApe (talk) 21:45, 17 December 2010 (UTC)


 * Yes, that is correct. Under Einstein's general relativity, time flows more slowly in a gravitational field.  See also our article on gravitational time dilation.  TenOfAllTrades(talk) 21:54, 17 December 2010 (UTC)


 * There are two different effects at work for the most famous clocks in space, the GPS system. 1) Being further from the Earth makes them run faster, gaining 45 microseconds each day.  2) Moving really fast in their orbits makes them run slower, losing 7 microseconds each day.  Combined, they would gain 45 - 7 = 38 microseconds each day.  Luckily, some smart people thought about this and made the necessary corrections.  Details.  --Sean 22:31, 17 December 2010 (UTC)


 * Gravitational time dilation is also the more important effect for satellites in geosynchronous orbit. But for something in a very low orbit, such as a space shuttle, relative velocity time dilation is the more important effect, so clocks on the space shuttle run slower than they do here on Earth.  To the right is a graph of how the two effects vary with orbital radius.  Red Act (talk) 22:47, 17 December 2010 (UTC)


 * The pyramids are no different than any other big chunk of rock in this respect. You might as well have mentioned Mount Rushmore. Even so, they're pretty much meaningless.  Even our entire planet only changes time by a handful of microseconds per day. The pyramids are minuscule in comparison. APL (talk) 03:06, 18 December 2010 (UTC)
 * I just plugged in some numbers into the equation for gravitational time dilation. Compared to a stationary clock far from anything, a clock at the surface of the sun runs slow by about 0.18 seconds per day.  So being next to the sun slows a clock so much that it's measurable with a cheap stopwatch.  Compared to a clock far from anything, a clock at the surface of the Earth runs 60 microseconds slower per day.  So being next to the Earth slows a clock by too little to measure with a stopwatch, but very easily enough to be measured with an atomic clock, which is accurate to about 10-9 seconds per day.  But a clock that's about 150 meters from the center of the Great Pyramid, which has a mass of about 5.9x109 kg, will only run about 2.4x10-15 seconds slower per day due to being next to the pyramid.  So being next to the Great Pyramid slows a clock by vastly too little to be measurable by even an atomic clock.  Red Act (talk) 08:28, 18 December 2010 (UTC)

My fuzzy potatoes
I bought a bag of sweet potatoes a couple weeks ago, and now they are moldy. I kept them in a cool place (around 60°F), so I was surprised by this. I frequently treat regular potatoes this way, and they don't rot nearly so quickly, but they do occasionally grow sprouts:

1) So, am I right in thinking that the regular potatoes stay alive after they are harvested, and that their immune systems stop decay, while sweet potatoes die and decay immediately thereafter ?

2) If so, what is it about normal potatoes that allows them to survive in my cupboard while sweet potatoes can't ?

3) I wanted to switch to sweet potatoes because they are more nutritious, but does this also make them more hospitable to mold ? StuRat (talk) 22:33, 17 December 2010 (UTC)
 * Moldy sweet potatoes and months-old "perpetual stew"? You won't need a pension. Re stew, see Bacillus_cereus 92.15.4.135 (talk) 14:08, 18 December 2010 (UTC)
 * Drench them in the same amount of anti-fungal treatment, ensure the RH is low and you probable wont notice any difference.--Aspro (talk) 23:28, 17 December 2010 (UTC)


 * RH ? Do you mean pH ?  And do they really treat normal potatoes with an anti-fungal agent ?  If so, why don't they use it on sweet potatoes, too ? StuRat (talk) 23:35, 17 December 2010 (UTC)
 * Relative Humidity. Roots store well if they are in a dry environment. It is pretty basic stuff they teach school girls in domestic science.--Aspro (talk) 00:16, 18 December 2010 (UTC)


 * Wikipedia even as an article -as it always does- on Domestic science. Wikipedia is an amazing resource, one should use it more often--Aspro (talk) 00:47, 18 December 2010 (UTC)


 * Mycotoxins are very harmful, You should throw them away and not eat them. Even the parts that look OK will have the toxins in them. 92.28.242.98 (talk) 23:57, 17 December 2010 (UTC)


 * Meh. Mold is everywhere, even if you can't see it.  Unless things turn soft and yucky, the usual solution is to just cut away the moldy parts. Looie496 (talk) 00:03, 18 December 2010 (UTC)
 * Professor Sir John Berry would disagree with you. Read the section "Benefits as ephemera" in his article here http://www.spiked-online.com/Articles/00000002D29C.htm Risk, science and society. Unfortunately the diagram seems to be missing. "...Derived from data reported by Mongeau et al (12) on the production of carcinogens (furocoumarins) in infected parsnips {but also applies to other moldy food}. Healthy roots produce little of these toxins, but when infected they are found in greatly increased amounts throughout the parsnip, not simply in the visually altered areas....Cutting out the damaged bits of spoiled vegetables is not sensible". I've noticed that people I assume to be North Americans have such an uncritical attitude to food; yet a large proportion of cancers, heart disease, strokes etc are the result of food choices made in previous decades. 92.15.4.135 (talk) 13:56, 18 December 2010 (UTC)
 * (EC with 92 and Looie4961) I'm not aware of that practise and I'm not sure what the heck is meant by RH. But to start at the beginning... our concepts of "dead" and "alive" are much blurrier for plants than they are for animals (which can also be tricky) and become downright irrelevant when you start talking about bits and pieces of plants. However, there is usually a period of continued metabolism (usually the transformation of starch into sugars) followed by either an extended period of dormancy or a breakdown of the plant material by outside action (i.e. mold, bugs, potato chip manufacturers, etc.) So, when you harvest a tuber, there are already a number of things going on: there are all manner of microorganisms that have set up shop, but which haven't yet taken hold, there is internal metabolism changing the more complex carbohydrates into sugars, and there is a small release of water vapour, etc. What the mold wants is a warm, dark, damp environment in which to get on with its business. Between the ground and your pantry, it doesn't get as many of things as it would like: the spuds spend time out in the dry air, there isn't that much sugar available, and the skin is relatively dry. But time goes on: sugars increase, there is a buildup of moisture, you've stuck the spuds in a dark drawer, and the metabolism within the tuber is warming it slightly. The longer the potato sits, the more optimum the conditions get for the mold to grow until the inevitable happens. So, why would your sweet potatoes get moldy faster? The same reason you call them sweet: five times the sugar content! And not only odes that give mold a leg up on a normal spud, sweet potatoes also come from further away, meaning they've been out of the ground longer, been in the dark of a ship's hold for longer, and so on. Matt Deres (talk) 00:07, 18 December 2010 (UTC)


 * PS - my reference for the "five times the sugar content" thing ended up getting blacklisted; Google sugar content potato versus sweet potato and you'll find it. Matt Deres (talk) 00:09, 18 December 2010 (UTC)


 * My sweet potatoes and yams store very well for months in the kitchen. Perhaps you kept them in a plastic bag or other container which retained moisture. In the rural US, historically they were very easy to keep all winter, longer than regular Irish potatoes or apples. They are hard and relatively dry and stay that way. Your post is very puzzling. Exactly how did you store them? Edison (talk) 00:51, 18 December 2010 (UTC)


 * You're right, I left them in the plastic bag I got from the store, but I've now removed the survivors and they are now in 20% humidity. Hopefully that will solve this prob. StuRat (talk) 05:14, 18 December 2010 (UTC)


 * My thoughts too! So, I reiterate what I posted above: Relative Humidity. Roots store well if they are in a dry environment. I reiterate: It is pretty basic stuff they teach school girls in domestic science.---Aspro (talk) 01:04, 18 December 2010 (UTC)


 * There was no need to reiterate and there would have been no need to explain yourself at all if you had simply been more helpful from the outset. Your snide condescension is also out of place. Matt Deres (talk) 01:31, 18 December 2010 (UTC)


 * Agreed. StuRat (talk) 05:11, 18 December 2010 (UTC)


 * One of the issues which has not been discussed is where the OP gought the sweet potatoes from? Unless you know the provenance of the potatoes, they could have been MONTHS old by the time you bought them.  A sweet potato which is a few hours out of the ground will likely be indistinguishable from one which is a few months out of the ground; there's no way to tell whether the sweet potato you bought at the SuperMegaMart has months of shelf-life left, or is just about to go off... -- Jayron  32  00:59, 18 December 2010 (UTC)

In a related Q, do sweet potatoes get worms ? Because some of them have a circular hole about a millimeter in diameter in them. At the store there were some small flying insects buzzing around them, so do the worms grow wings when they mature ? StuRat (talk) 05:22, 18 December 2010 (UTC)
 * I don't see why not. There are literally too many possible flys and their associated maggots to name which may infest sweet potatoes.  Maybe some type of Drosophilidae?  -- Jayron  32  06:55, 18 December 2010 (UTC)


 * Note that potatoes are an Andean crop which survives the winter underground. In regions subject to the depredations of war or oppressing armies (such as Ireland) they were often harvested throughout the winter so that a military force couldn't effectively seize them from the populace.  And of course seed potatoes can be chopped up and replanted.  So the life of the potato, under normal circumstances, really isn't in doubt. Wnt (talk) 05:17, 19 December 2010 (UTC)


 * The conversation is not about potatoes, it's about sweet potatoes. Sweet potatoes (Ipomoea batatassometimes, sometimes called yams, but unrelated to yams) are more closely related to morning glories than they are to "regular" potatoes (Solanum tuberosum, which are closely related to tomatoes and other members of the nightshade family). Their only shared similarity (versus non-"potato" plants) is that they both have starchy underground tubers that humans dig up and eat. Even then they're not really all that similar, as a a sweet potato is a root tuber, while a regular potato is a stem tuber/stolon. -- 174.24.216.113 (talk) 18:16, 19 December 2010 (UTC)