Wikipedia:Reference desk/Archives/Science/2006 September 1

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nature cure

respected whomsoever,i am a naturopathy and would like to have answer for a question in water therpy of nature cure. "Why do we use cold water therapy?" I need to have a scientific approach to this answer

We need to have a slightly more detailed question.--Light current 03:41, 1 September 2006 (UTC)

this could be interesting, given naturopathy and science are pretty much mutually exclusive Xcomradex 03:56, 1 September 2006 (UTC)

Check out Hydrotherapy for history and techniques, Naturopathy for references to scientific (and governmental) assessment.---Sluzzelin 05:42, 1 September 2006 (UTC)

Unknown green insect

What is this insect? Which species, family, or order? The photo was taken in Gyeonggi-do, South Korea. --Kjoonlee 03:24, 1 September 2006 (UTC)

Some type of walking leaf, I would guess. Here's a pic of the Malaysian Walking Leaf: [1]. StuRat 03:34, 1 September 2006 (UTC)

I give up, this ones too hard. I'm guessing that the two front legs are held up in front of it's face or something, but I can't find anything like that with a flat back, and I've just sifted through a few thousand images. It seems leaf insect is a bit more technical than walking leaf, though they both refer to the (huge) Phasmatodea (and the possibly more relevant Phylliidae) anyways.  freshofftheufoΓΛĿЌ  12:40, 1 September 2006 (UTC)

Thank you. :) According to SNU's insect taxonomy website, It's Neotituria kongosana. Here are some other photos: [2] --Kjoonlee 13:31, 1 September 2006 (UTC)

A sort of leafhopper. Cicadellidae, Ledrinae, Petalocephalini, Neotituria kongosana. --Kjoonlee 13:46, 1 September 2006 (UTC)

I susupected it was some sort of leaf hopper, but I couldn't find any that had such a flat shell structure. Most of them seem to look like the first 2 in that link you gave. All of my sources were English, though, and about 99% of the images were from the US, so I guess that explains why I couldn't get any closer : (.  freshofftheufoΓΛĿЌ  06:59, 2 September 2006 (UTC)

Hoodia Gordonii

What is it and how does it work and how much of it do you take?

See Hoodia. Melchoir 04:41, 1 September 2006 (UTC)

Hoodia trust for medical advice? Edison 17:01, 1 September 2006 (UTC)

neutron star

what is a neytron star.is it possible to get some or addsome neutron in that star?

All is revealed at neutron star. Search first; it's quicker.--Shantavira 06:18, 1 September 2006 (UTC)

First make sure you understand your own question, though. DirkvdM 09:34, 1 September 2006 (UTC)

anaytrunstar is a starthat is not tronn but instedaq it is neytron.mickjagger is arock star...if he had some neyutron maybe heedbe a neutron start Loomis 21:01, 3 September 2006 (UTC)

medical

If an injured swimmer was to drown and the red blood cells found in the lungs were swollen and had burst, did the person drown in fresh water or sea water? Given that the tonicity of sea water is greater than that of the cytoplasm of blood cells , and the tonicity of fresh water is less than that of red blood cells, explain how you reached your conclusion. What process has occured in this situation? thanks Johanna

Sorry, you should probably do your own homework. Tonicity might be a good place to start. -- Plutortalkcontribs 12:27, 1 September 2006 (UTC)

Actually, you should ask for better homework questions. People who drown have water in their lungs, not blood. Their blood is in their circulatory systems, before, during, and after drowning. The question should allude to lysis of RBCs within the lung capillaries, not "in the lungs". Freshwater is hypotonic and flows rapidly through the pulmonary capillaries overloading the heart and causing lysis of RBCs with K⁺ release. Death is rapid. Saltwater is hypertonic and there is no mass fluid transfer; death is slower and has a strong asphyxial component. - Nunh-huh 21:08, 1 September 2006 (UTC)

There are lots of ways to die of immersion, including sudden arrest, air embolization, asphyxial suffocation without water inhalation, etc. See [3] for a fairly good overview. The question is easy based on test-taking skills: the questioner is obviously ignorant about drowning and doesnt care about drowning but wants to see if you understand the isolated concept of hypotonic versus hypertonic fluid effects on rbcs. The question would be the same if they asked what would happen to rbcs dropped into a hypotonic or a hypertonic solution.alteripse 23:55, 1 September 2006 (UTC)

Difference between PRECISION & ACURRACY?

What is the clear-cut distinction between precision & accuracy?

• Accuracy and precision. Weregerbil 12:58, 1 September 2006 (UTC)

A nice example is that if I said I was 6.32456m tall, it would be high precision but low accuracy. If I said I was 1.5m tall, it would be less precise, but more accurate. —Daniel (‽) 13:13, 1 September 2006 (UTC)

Why. How tall are you?--Light current 20:42, 1 September 2006 (UTC)

Assuming that the number of figures is used as an indicator of the precision. —Bromskloss 13:50, 1 September 2006 (UTC)

It ought to be, when reporting a measurement. See significant figures. TenOfAllTrades(talk) 15:24, 1 September 2006 (UTC)

Well, the real difference, is that PRECISION is what they ask you in about in a freshman lab course, where as ACURRACY is what they ask you about in lecture, 2 completly different types of homework you want us to do for you--71.247.243.173 19:03, 1 September 2006 (UTC)

Kid in a natural history museum: "Hey mister, how old is that dinosaur ?"

Guard: "200 million and 8 years old."

Kid: "You mean 208 million years old ?"

Guard: "No, I mean 200 million and 8."

Kid: "But how do you know so precisely ?"

Guard: "Well, it was 200 million years old when I started working here 8 years ago, so..."

StuRat 00:59, 2 September 2006 (UTC)

Another way of thinking about precision vs. accuracy is that, even though you were inaccurate when you mis-spelled accuracy as acurracy, we still knew precisely what you meant. JackofOz 12:35, 3 September 2006 (UTC)

Should this one be on the language RefDesk, Stu? :) Loomis 20:57, 3 September 2006 (UTC)

No, because they are simply synonyms in general English, it's only in the scientific area where the definitions differ. StuRat 08:47, 4 September 2006 (UTC)

Accurate: acceptable, truthful value. Precise: Getting the same value repeatedly. --Proficient 17:31, 4 September 2006 (UTC)

I wouldn't say they're synonyms in English. For example, it would be a very accurate but very imprecise statement to say that roughly a bit more than half of the human population is female, whereas it would be a very precise yet very innacurate statement to say that precisely 48.563982% of the world population is female. Also, one can say "I want you to be at my office at precisely 11:42am", whereas the statement "I want you to be at my office accurately at 11:42am" wouldn't seem to make much sense at all. Loomis 08:33, 6 September 2006 (UTC)

You are using the math/science meanings. A plain English usage might be "he is admired for the precision/accuracy of his Oscar picks". StuRat 07:36, 7 September 2006 (UTC)

Another example: My chemistry teacher said that 1 litre and 1.00 litre of a particular liquid mean different things. The reason: 1 litre meant was that you had between 0.5 and 1.5 litres. 1.00 litres actually meant that you had between 0.995 and 1.005 litres. Maybe precision is whether you use 1, 1.0 or 1.00, and accuracy is whether you measure it to be 0.997, 1.001 or 1.003? -- Chuq 10:18, 6 September 2006 (UTC)

The level of "Precision" seems to be concerned more with the level of detail, and far less concerned with the veracity of a statement, whereas "Accuracy" tends to far more concerned with veracity, and far less concerned with detail. Loomis 22:32, 6 September 2006 (UTC)

Cattle in a feedlot

I know that before slaughter, many cattle are housed in a feedlot to be fattened up. I would like to know about how long an animal will typically stay in the feedlot. ike9898 13:08, 1 September 2006 (UTC)

According to this page that used to be on Harris Feeding Company's website, "cattle typically spend approximately 12 to 16 months grazing; then, at 650 to 750 pounds, enter the feedlot for about 3 to 4 months to gain an additional 400 pounds or so." -- Plutortalkcontribs 15:00, 1 September 2006 (UTC)

Could you add that to the article? Rmhermen 16:51, 1 September 2006 (UTC)

Yeah, I'm also trying to find another source. ike9898 20:37, 1 September 2006 (UTC)

Acetone as an additive for gas and diesel?

I read that adding minimal amounts of acetone to gasoline and diesel would increase mileage considerably. My question is if that is really the case. Also, of course, the car should not get damaged if one were to do this (especially the catalyst). Last but not least, would this increase, decrease or not affect exhausts at all? Thanks for your answers, RichiH 13:25, 1 September 2006 (UTC)

Off the top of my head, I can't think of any reason why acetone should improve mileage, mile per joule, more than any other fuel, so it sounds wrong to me. Again, off the top of my head, the only additives that make a difference to engine operation beyond their calorific value are things that affect the octane rating of the fuel (and they really affect smoothness of operation rather than efficiency), and I can't see acetone doing this.

Catalysts are primarily damaged by lead additives which coat the Pt/Pd, acetone certainly wouldn't do this.

The major problem I see with using acetone as a fuel is that it mixes with water, so using pure acetone would mean having water in the engine which would corrode it. Same reason why you dont use washing-up liquid as a lubricant, even though it's ideal in most other respects.

Actually this is an advantage. Having Acetone absorb the water and carry it through the engine is a good thing, unless you are talking about a lot of water. 12.41.204.3

No it isn't. You shouldn't contribute to topics in which you have no formal knowledge, particularly to contradict people who have. You've also been told before to sign your comments. Rentwa 17:21, 1 September 2006 (UTC)

The burnt acetone would come out in the exhaust just like the other burnt chemicals - it wouldn't have any disproportionate effect on exhaust.

If you can provide a link to the original article or quote it, it might help. Rentwa 13:54, 1 September 2006 (UTC)

I would have provided the link, but it's on another box and i do not have access to that, right now :/ RichiH 18:04, 2 September 2006 (UTC)

I think i found the page, again: [4]. Googling also showed this: [5] which points to here: [6] RichiH 18:18, 2 September 2006 (UTC)

Thanks Richi. The molecular theory sounds pretty good (so did the theoretical explanations of Cold Fusion). Petrol/Diesel are mostly hydrocarbons, like sticking to each other, don't like sticking to acetone. Mix a bit of acetone in and it breaks up the whole thing, so there's a lot less sticking going on. And hey presto, the fuel is easier to vapourise, burns more efficiently etc etc.

However, from a thermodynamic point of view this is saying that a little drop of acetone is doing one hell of a lot of work - it's like putting a drop of something into a cup of water and the water boiling. You can get a rough idea of the amount of free/magic work the acetone is supposed to do from the claimed fuel efficieny improvements (laughable). And since the claim refers to this special mixture having more potential energy than the fuel and acetone independently, for it to work the exhaust gasses exiting the engine would have to be different in some way from a mixture of burnt fuel and acetone, and obviously they won't be. So complete bollocks. :) Rentwa 19:21, 2 September 2006 (UTC)

The third source tries to claim that atomisation (better description than vapourisation) is incomplete and fuel is wasted - not true. Modern engines, especially with engine management systems tend to run at trace knock (lean burn) - no significant unburnt fuel. And since the catalyst is effectively a final combustion chamber, if there was any large amount of unburnt fuel the catalyst would be getting very hot indeed. Finally, molecular vibrations aren't relevant to the discussion on the mixture, polarity is, and I've never heard a real scientist talk about sluggish molecules or 'natural frequencies'. Total bollocks! Rentwa 21:21, 2 September 2006 (UTC)

Thanks Rentwa, i did think it sounded too good to be true. Still, a pity ;) RichiH 12:40, 3 September 2006 (UTC)

The acetone thing is an urban legend. Mythbusters even tackled it--it doesn't work. All it will do is damage your paint job if you spill... -- Scientizzle 14:22, 1 September 2006 (UTC)

It would definately hurt your paint job as nail and car paint are very similar. I even tried this, once. (No, not on a car.. ;) RichiH 18:04, 2 September 2006 (UTC)

I can't see how acetone would help; I can see how it would hurt. It's combustion properties are going to be different from gasoline (I can't be bothered to dig out exactly how, at the moment) so it will burn hotter/faster or colder/slower than gasoline. Adding it into the mix in any concentration high enough to have an effect is either going to result in added wear and tear on the engine and increased output of nitrogen oxides (if it burns hotter) or incomplete combustion and increased output of unburned fuel, soot, and carbon monoxide (if it burns colder). Acetone may also attack engine components, as Rentwa notes it will allow water into the fuel, and it will probably harm the finish on the car if spilled. Finally, acetone has a much higher vapour pressure than regular gasoline, resulting in greater losses to atmosphere during filling and increased risks when used in confined spaces. TenOfAllTrades(talk) 15:22, 1 September 2006 (UTC)

Acetone burns faster, thus it should reduce the octane value imho RichiH 18:04, 2 September 2006 (UTC)

If there are plastic parts or hoses which degrade, soften or dissolve in acetone but not in gasoline, you might be in for some expensive repairs. As an analogy, I had a 1970 GM engine which worked great until in the 1980's they started adding alcohol to gasoline. The alcohol ruined the plastic float in the carbureter and required replacement of the carb. And doesn't acetone react with copper? Gasoline is for burning in engines, alcohol is for drinking, and acetone is for removing nail polish. Edison 17:06, 1 September 2006 (UTC)

As Edison shows above, chemicals are used for specific things for a reason. I wish I could explain why acetone is used the way it is, but I've only experienced organic chem for 2 classes so far :/ --Russoc4 20:05, 1 September 2006 (UTC)

genetics

do all the somatic cells in our body have the same sequence of DNA?--hima 13:30, 1 September 2006 (UTC)

In theory they all should since they are all clones. In practice, however, mitosis does not copy with 100% accuracy so there are differences. Add Lyonization and DNA methylation to the mix, you have quite a few differences. InvictaHOG 13:57, 1 September 2006 (UTC)

Also, some people are chimeras, but that's rare. --Allen 03:55, 2 September 2006 (UTC)

Article in Dec 2000 Cleo

I am looking for an article you had in Dec 2000 Cleo titled FLEX by Sam Murphy. It was four pages long and was about exercises for deep abdominal muscles. If there is anyway you could forward me a copy or put it on your website I would be most grateful. Thank you Ruth Kelly, Ireland.

Wikipedia does not publish nor maintain archives of Cleo (magazine), but we have a stub article on it... Perhaps this should be moved to Humanities?Nimur 19:40, 1 September 2006 (UTC)

potentiometer

Q1 principle of potentiometer? Q2 why voltage decreases in the direction of electric field? (please explain in detail) thankyou.

A1 potentiometer / A2 voltage drop ---Sluzzelin 13:58, 1 September 2006 (UTC)

A2 Consider a line through an electric field, with three points on it, A, B, and C. The voltage at A is 2V, at B it is 1 V, and at C it is 0 V.

A-----------B---------C

If an object initially at rest, with a charge of +1 coulomb moves from A to C in an environment with no friction or other impediment, it will acquire kinetic energy of 2 joules by the time it gets to C. On the other hand, if the object starts at B, it will only have 1 joule of kinetic energy when it gets to C. So the voltage at any point in an electric field is a measure of how much energy a charged particle will acquire as it moves through an electric field, and the less of the field it moves through, the less energy it will acquire. --Gerry Ashton 16:32, 1 September 2006 (UTC)

mosquito

what does a mosquito have instead of blood is it hemolymph like all other insects?or anything else?--hima 13:56, 1 September 2006 (UTC)hima

Have a look at mosquito and hemolymph --Light current 14:24, 1 September 2006 (UTC)

Hemolymph redirects to blood or circulatory system. We don't have much of an article on it, just a few sentances in the appriate article. — [Mac Davis] (talk) (Desk|Help me improve)

Petrol additives

Is there anything that can be added to unleaded petrol to improve fuel consumption in a car with an engine management system? —Preceding unsigned comment added by Light current (talk • contribs)

I don't think so. It would be more productive trying to tweak the software I think.

In the UK you can add vegetable oil to your diesel fuel (or run pure veg oil) - veg oil is untaxed so it's cheaper than diesel and works just the same. You can smell cars running on veg oil as they drive past - not a myth at all. Illegal though. Rentwa 14:47, 1 September 2006 (UTC)

Vegoil as fuel is taxed in the UK now: see vegetable oil as fuel. Rmhermen 16:48, 1 September 2006 (UTC)

Motorists have always been liable to pay tax and duty on the fuels they put in their cars. There's nothing illegal about putting veg oil in your car - it's illegal not send a cheque to the chancellor when you do so, which most veg oil drivers don't. Veg oil for sale in the supermarket has no fuel duty or tax added to its price, or housewives would probably be complaining... Rentwa 17:40, 1 September 2006 (UTC)

In Germany, running on vegoil is not taxed and a more and more common option for diesel cars. Please note that you should consider installing a dual system with a large vegoil tank and a small diesel tank. The first and last 15 minutes of any trip should be done on diesel to prevent clogging of the pump etc. This is especially important in cold climate! RichiH 13:35, 3 September 2006 (UTC)

Most of the additives sold to mix in with your fuel and oil are modern-day snake oil, except in the relatively rare case where your fuel system is genuinely clogged. Subaru recommends the occasional use of an injector cleaner in the fuel of my car, but other cars I've owned have not done so.

One possibility is buying petrol with a partial ethanol blend; it's cheaper in some places because there's no taxes on the ethanol part. But the savings, if any, will be very small.

If you really want to save fuel, make sure you don't carry unnecessary items in the car, make sure your tires are kept inflated to the recommended pressures (or a little above, perhaps to what the manufacturer recommends for heavy loads), and drive smoothly and at sensible speeds. Beyond that, drive a more fuel-efficient car. -Robert Merkel 15:47, 1 September 2006 (UTC)

Could it be my EMS sensors not working correctly?--Light current 15:51, 1 September 2006 (UTC)

In your car I think the problem is less likely to be caused by hardware or software, and more likely to be something to do with the wetware. :D Only kidding :) . Rentwa 18:32, 1 September 2006 (UTC)

Well, additives do reduce gasoline consumption in that they burn themselves, providing some fuel. So, if you add a pint of fuel additive to a tank of fuel, you might reduce the fuel consumption by up to a pint. Thus, they aren't lying when they say their additive "reduces gasoline consumption", they are technically correct. Of course, the cost of the additive greatly exceeds the cost of the saved gasoline, that part they don't tell you. StuRat 00:49, 2 September 2006 (UTC)

World spin

Ive often wondered what originally gave rise to the rotation of the earth and what its rotational energy would be. Any one know?--Light current 15:12, 1 September 2006 (UTC)

I am guessing, but most of the planets rotate in the same direction the Sun does, right? So the theory is they arose from a gout of matter spouting from the sun which condensed into what we have today. They also rotate in the same direction they revolve around the Sun, too, right? 12.41.204.3

Not necessarily. The original nebula from which the Sun formed had angular momentum, and following the prevalent theory of planetary formation, the entire cloud was rotating (perhaps due to the supernova explosion that gave birth to the cloud to begin with), and the planets, as they coalesced by attracting all the objects within their gravitational field and colliding among themselves, maintained that angular momentum. Titoxd^(?!?) 17:02, 1 September 2006 (UTC)

After edit conflict:

As was discussed in a thread a few days ago, Venus and Uranus are the odd ones out when it comes to rotation. The rotational direction of the others makes sense to me in the way the coriolis effect works: material that moved from the outside of the accretion disk towards the inside to become part of the Earth went to a region with slower rotation, so the material that hit the part of the Earth that was pointing away from the Sun moved faster than the Earth and thus gave that side an extra impulse. Material that came from the other side ('from the Sun') was slower and thus slowed that side of the Earth down. DirkvdM 17:17, 1 September 2006 (UTC)

Calculating the rotational energy would require integration, which I'm not good at, so I'll just make an educated estimation. A kg at the equator moves at 40.000 km / 24 h and thus has an an impulse of 40.000.000 m / 80.000 s = 500 kg.m/s. The Earth weighs 6 x 10²⁴kg and assuming that the centre of mass of one side is at about half the radius the total rotational impulse would be 0,5 x 6 x 10²⁴ x 500 = 1500 x 10²⁴ kg.m/s. That's impulse, though, not energy. I'm not a physicist either. :) DirkvdM 17:25, 1 September 2006 (UTC)

Don't forget to include moons and rings when calculating the orbital angular momentum of a planetary system! Nimur 19:36, 1 September 2006 (UTC)

Moons and rings are typically insignificant in mass compared with the planet they orbit. Earth's moon is an exception, being quite large relative to Earth. Pluto, if you still consider it to be a planet, is also an exception, with it's biggest moon, Charon, being even larger relative to Pluto than our moon is to Earth. The mass of everything else in the solar system is also insignificant relative to the Sun. StuRat 20:44, 1 September 2006 (UTC)

Well early earth collided with a "roughly mars sized object" so wouldnt its spin be messed up this anyway? Philc _T^E_C^I 20:56, 1 September 2006 (UTC)

The Giant impact theory? Not necessarily. If the two bodies were rotating on similar planes, they would have a very similar angular momentum unit vector, so when the collision occured, the resulting body would still have the sum of the individual bodies' angular momentum, in a similar direction. Titoxd^(?!?) 06:10, 2 September 2006 (UTC)

I don't think similar planes would do it, they would have to be orbiting in pretty much exactly the same plane, or the off-center collision would tilt the two rotating objects. StuRat 10:32, 2 September 2006 (UTC)

Since they didnt collide core to core, and more of glanced, tearing the smaller in to 2 pieces, one of which then collapsed into the earth, the other settled into orbit after taking a large lump of crust with it. Aglancing hit would mean al of the momentum was transferred onto one side, so would it actually be possible for the spin to be undisturbed. Philc _T^E_C^I 18:58, 2 September 2006 (UTC)

The rotational kinetic energy is actually easy to calculate (treating the Earth as a sphere allows us to re-use others' integration!), and is even given in that article as an example. --Tardis 17:56, 6 September 2006 (UTC)

Zoosex

Can for example a cat become pregnant from human sperm and vice versa (a woman from horse)? --Brand спойт 16:55, 1 September 2006 (UTC)

'Can for example a cat become pregnant from human sperm ...' is there something you want to tell us? Rentwa 17:45, 1 September 2006 (UTC)

Unless they contain the same number of chromosomes, no. Titoxd^(?!?) 16:58, 1 September 2006 (UTC)

not entirely true -- as mentioned below, horses and donkeys can reproduce, even tho they have different chromosome numbers. if they have a different no of chromosomes, tho, their offspring will almost certainly be infertile --DakAD 07:23, 3 September 2006 (UTC)

Their offspring will always and without execption be infertile. RichiH 13:39, 3 September 2006 (UTC)

Oopsie, seems a ; instead of : in the identation makes text bold.. RichiH 14:26, 3 September 2006 (UTC)

No. Species must be very similar for such matters to take place (horse and donkey, for example). —Daniel (‽) 17:00, 1 September 2006 (UTC)

Also supposedly lion and tiger. What about primates? Gorilla/chimp/orangutan combinations? Horse/zebra? Edison 17:11, 1 September 2006 (UTC)

Species are defined as being able to interbreed, so if two animals are of different species, they can by definition not interbreed. Btw, if you ask about interbreeding primates, why not take a combination with humans to spice it up a bit? A humanzee? A humilla? With an Orang Utan the naming gets interresting because the word 'orang' is Indonesian for 'human' (and 'hutan' means forest, so it's a 'forest man'). DirkvdM 17:33, 1 September 2006 (UTC)

It's a little more complicated than that. Horses and donkeys are definitely different species, but they can produce offspring, and once in a great while even fertile offspring. Sometimes species are defined as being able to produce offspring that "breed true", whatever that means. I think it needs to be recognized that there is no completely precise biological definition of "species"; like any other level of taxonomy, there are arguable borderline cases. --Trovatore 17:37, 1 September 2006 (UTC)

If it is seperate genuses than no way, as far as I know. — [Mac Davis] (talk) (Desk|Help me improve)

For the record, the plural is "genera", à la generic vs. specific characteristics. Melchoir 18:13, 1 September 2006 (UTC)

Yes there are cross-genera and even cross-family hybrids. See hybrid, the article. Rmhermen 18:48, 1 September 2006 (UTC)

Two separate geniuses have indeed been known to reproduce. Edison 04:51, 2 September 2006 (UTC)

animal genera? --DakAD 07:23, 3 September 2006 (UTC)

I see a pattern emerging here. First, there was no precise definition of planet until last week (and it's still not fully accepted). Now, you're telling us there's not even a precise definition of species. Before we go any further, is there anything else the scientific world wishes to 'fess up about? JackofOz 12:28, 3 September 2006 (UTC)

To get back to the original question, rest assured, no, your cat is absolutely, positively, not pregnant with your love-child. Loomis 20:54, 3 September 2006 (UTC)

You mean love kitten!--Light current 20:56, 3 September 2006 (UTC)

Humans can't even make a chimpanzee or bonobo pregnant, so there's not very much to worry about. However, according to Greek mythology, the minotaur was born when a woman hid into a wooden cow to mate with a bull that she loved. bibliomaniac15 23:48, 5 September 2006 (UTC)

Citric Acid

Would diluted citric acid kill sperm?

Are we still talking about the cat? Rentwa 18:40, 1 September 2006 (UTC)

Ah, but aren't we all, on some level, talking about the cat? Melchoir 18:43, 1 September 2006 (UTC)

I think the cat is really going to dislike you if you introduce citric acid to the sitution. Weregerbil 18:55, 1 September 2006 (UTC)

Would diluted citric acid kill the cat? Until we dump the citric acid on the cat, he is both alive AND dead; we will determine an outcome by dumping acid on him. DO NOT TRY AT HOME Nimur 19:35, 1 September 2006 (UTC)

It probably wouldn't kill the cat, but I bet it would sting the pussy. Rentwa 00:01, 2 September 2006 (UTC)

Oooo it makes your eyes water just to think about it (2 points I think 8-))—Preceding unsigned comment added by Light current (talk • contribs)

This is a surprise to me, but Spermicide actually answers the question. Melchoir 18:44, 1 September 2006 (UTC)

Not talking about the cat (though funny placement. I have good timing.) Thanks!

Err...Part two; would citric acid kill a yeast infection?

Dammit, I can't look at that article. I'm not even going to link to it. Melchoir 19:58, 1 September 2006 (UTC)

Which article do you mean?--Light current 01:59, 2 September 2006 (UTC)

Why not try squeeezing your lemon to find out?--Light current 21:33, 1 September 2006 (UTC)

"Squeeze my lemon, till the juice runs down my legs". DirkvdM 09:19, 2 September 2006 (UTC)

Did you catch the yeast infection from the cat? You should probably see a doctor, or Vet..........Daniel.thorpe 11:08, 5 September 2006 (UTC)

Moon moons ?

Does any moon have it's own natural satellites ? I would expect they would, unless tidal forces from the planet would cause their orbits to be unstable.

If there are examples of moon moons, how about moon moon moons, etc. ? (Has the word lost all meaning yet ?) :-) StuRat 20:49, 1 September 2006 (UTC)

Wouldnt any moon moons be pulled out of their orbit when they get to close to the planet of the moon they are orbiting, as relative to their sizes, planets are alot closer to their moons, than the sun is to its.

Hmm... isn't that what happens at a Lagrange point? And it sounds a bit like something the L5 Society would like to know. Titoxd^(?!?) 20:57, 1 September 2006 (UTC)

Do you consider 3:2 orbital resonance to be a "moon"? (Earth's "second moon" is 3753 Cruithne, which is not really a moon but has a 1:1 resonance.) Then Pluto would be a moon of Neptune, and then Nix and Hydra are "moon moons". —AySz88\^-^ 21:08, 1 September 2006 (UTC)

It would be extremely unlikely that any moon would have its own moons. Any such orbits would be extremely unstable with all the bodies as close together as they are in a solar system. Over larger distances it's certainly possible, although the bodies get a lot bigger. The Sun orbits the centre of the galaxy, the Earth orbits the Sun and the Moon orbits the Earth. Why this system works is probably best explained by the anthropic principle. An alternative explanation would take a very long time to give.

I think if you have too many generations of moons, you may end up with an ustable chaotic system that would eventually chause some of thes objects to coalesce.--Light current 14:51, 2 September 2006 (UTC)

---

What conditions would be needed to have a stable moon moon ? Perhaps a huge planet/failed star at an extreme distance (say 40 AU) from the main star could have a moon at an extreme distance from it (say 1 AU), and a moon moon around it that would be stable (being far enough away from gravitational tidal forces of the planet and star) ? StuRat 00:34, 2 September 2006 (UTC)

Although I don't know of any, I don't see why in theory moons can't have moons. After all, our moon has over the past half century had probably hundreds of "artificial satellites" orbitting it. Though these artificial satellites have generally, deliberately ended there missions by having their orbits decay, eventually crashing into the moon, surely there must be at least some space junk orbitting the moon at this time in an orbit with the potential to carry on indefinitely. This may be "space junk", but if it exists, in theory at least, it would seem to qualify as a "moon" orbitting the "moon". Loomis 04:24, 2 September 2006 (UTC)

Isn't that a matter of mass? An artificial satelite can do it, so why not a natural one? How this would be formed is a differnt matter. I don't think you would get such a moon from the same planetary accretion disk, so it would have to be caught. Probably the chances of that producing a stable orbit are very small, but in an immense Universe that's all you need. DirkvdM 09:28, 2 September 2006 (UTC)

In theory moons can have moons. The problem is that the orbits will (almost) certainly be unstable over long time periods due to the number of forces acting on them (they would certainly be unstable if they existed for an infinite time). It is possible (although highly unlikely) that (taking our moon as an example) our moon could trap a body to behave as its own satellite, but it would only stay there for a very short time and, if it did happen, we weren't around to see it. Artificial satellites have the same problem of stability. The articles on chaos and the n-body problem should be relevant to this (assuming they're well written).

Moons can have artificial satellites, such as the Apollo Command/Service Module during the manned moon missions. Nimur 13:03, 2 September 2006 (UTC)

Just to qualify everything... in the approximation that the moon's orbit is circular, then you can prove mathematically that certain orbits around the moon are stable, since they are completely encircled by the zero-velocity curves of their Jacobi integral. Such protective curves go all the way out to the nearest Lagrange points. So you don't have to worry about the planet pulling the particle away from the moon.

What you do have to worry about is the possibility that, if you wait long enough, the particle might crash into the moon. There is no mathematical barrier to such a crash, as there is in the two-body problem (the centrifugal barrier). In some sense the real question is, how long should it take for such a crash to occur? And I seriously doubt there's a known analytic answer to that one; you'd have to break out a numerical simulation, plug in your desired mass ratio and moon radius, and see. Melchoir 17:23, 2 September 2006 (UTC)

I could always moon the Moon. Would that help? Clarityfiend 04:37, 3 September 2006 (UTC)

And then let someone else drop their pants and run in circles around you. Problem solved. QEI (quod erat inquisitum). DirkvdM 05:36, 3 September 2006 (UTC)

Private Hospitals in Altanta, Georgia in existence 1967

Trying to locate nurse who worked in expensive private hospital, Coronary Care Division in Atlanta, Ga. in 1967. Hospital could place instrument for heart (cost $2,000) on arm in case of heart failure. Feel this fairly new concept at time. Hospital's name wanted. Help,please!

How about Emory University hospital? InvictaHOG 21:24, 1 September 2006 (UTC)

Free software to make contour maps from spot heights?

Is there any please? There is a pay-for program called Surfer, but it costs over $500. 62.253.44.32 23:36, 1 September 2006 (UTC)

Given an XY grid of points, where the Z coord is given for each, it seems like quite a simple program could create a contour map. Given points not on a grid, it would be a bit trickier. Also note that a general 3D CAD system could do this, by running a surface thru a point cloud, then intersecting that surface with planes parallel to the XY plane. StuRat 00:23, 2 September 2006 (UTC)

Wouldnt it be grossly inaccurate due to the fact that the ground is not flat planes between spotheights, something that a program designed for this would probably take into account. Philc _T^E_C^I 00:33, 2 September 2006 (UTC)

The simplest program could just do a linear interpolation between grid points, to find contour line/grid line intersection points, then draw straight lines between those. For example, given grid point elevations of 4, 6, 7, 1, 2, and 4, a contour line could be drawn at an elevation of 5:

4 . . . . . * . . . . . 6 . . . . . . . . . . . 7
. . . . . . . . * . . . . . . . . . . . . . . . .
. . . . . . . . . . * . . . . . . . . . . . . . .
. . . . . . . . . . . . * . . . . . . . . . . . .
. . . . . . . . . . . . . . * . . . . . . . . . .
. . . . . . . . . . . . . . . . * . . . . . . . .
. . . . . . . . . . . . . . . . . . * . . . . . .
. . . . . . . . . . . . . . . . . . . . . * . . .
. . . . . . . . . . . . . . . . . . . . . . . . *
. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . 
1 . . . . . . . . . . . 2 . . . . . . . . . . . 4

StuRat 03:27, 2 September 2006 (UTC)

R is free and can make contour maps, I'm pretty sure. I don't know fancy the graphics get, though. --Allen 03:46, 2 September 2006 (UTC)

Gnuplot can produce contour plots. – b_jonas 10:42, 2 September 2006 (UTC) (Update: I mean if the samples form a grid. – b_jonas 10:43, 2 September 2006 (UTC))

Thanks, but unfortunately my data does not form a grid.

If the data is not already in a grid, the first task of any program would be to establish a grid, a process called tesselation. Then you could do the same linear approximation discussed previously, from there. However, if you only have a low number of sample points, the resulting contour plot will be highly inaccurate. StuRat 03:06, 3 September 2006 (UTC)

I believe that Yorick programming language can produce contours from data on irregular meshes. But just trying to understand that part of its documentation makes my head hurt. -- The Photon 04:51, 4 September 2006 (UTC)

Hmmmn, I wonder if the best method would be to assume that the height at any point would be the weighted average of all the spot heights, where the weights are in inverse proportion to the distance (or perhaps distance squared or some other weighting scheme)?

If I were to implement this myself rather than use somebody elses software, then the question changes to: Whats the best way to interpolate heights from know spot heights? Thanks again.

I think you've got a good idea for how to do it. I do see one problem, though, you could never get a height above the max input height or below the min input height. Consider these data points:

Z *                       *
^   *                   *  
|      *             *
|              
+---------------------------> X

The result of the extrapolation should provide this point:

Z *                       *
^   *                   *  
|      *             *
|             * 
+---------------------------> X

StuRat 11:58, 3 September 2006 (UTC)

Yes. This reminds me of kriging or splines, although I've no idea if either free software is available or how I could implement these myself.

Sorry to be pedantic, but shouldnt you have said interpolation?--Light current 20:59, 3 September 2006 (UTC)

Well, interpolation would be correct if I only meant to describe filling in between data points, but I also meant filling in beyond the end of the data points, so extrapolation covers both cases:

Z *                  
^   *                  
|      *             
|             * 
+---------------> X

StuRat 08:40, 4 September 2006 (UTC)

You might be interested in checking these discussions http://stackoverflow.com/questions/11449214/creating-grid-and-interpolating-x-y-z-for-contour-plot-sagemath http://in.mathworks.com/help/matlab/math/interpolating-scattered-data.html http://stackoverflow.com/questions/19339296/plotting-contours-on-an-irregular-grid Shyamal PS: silly me to edit on an old archive page that I had accidentally opened!!! (talk) 08:53, 30 January 2015 (UTC)