Wikipedia:Reference desk/Archives/Science/2010 November 20

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November 20

Entropy gun?

Would it be possible to make a weapon that shoots pure entropy? If so, why hasn't it been done? Blobs of entropy would be able to go through any type of protective shielding by scrambling the particles in the matter when it hit. --75.33.217.61 (talk) 00:13, 20 November 2010 (UTC)

Entropy isn't a substance. It's similarly not possible to make a gun that shoots pure inertia, or viscosity, or prettiness. Paul (Stansifer) 00:16, 20 November 2010 (UTC)

But would it still be possible to make a weapon that generates large amounts of entropy, even if it isn't pure? The second law of thermodynamics should make that easy. --75.33.217.61 (talk) 00:23, 20 November 2010 (UTC)

All explosives, in effect, increase the local entropy wherever they go off. That's why it is easier to blow things up than it is to put them together. --Mr.98 (talk) 00:25, 20 November 2010 (UTC)

Entropy is a measure of disorder. The more disordered something is the larger is its entropy. What you're suggesting is like designing a gun that shoots kilometers (or miles, if you're that way inclined), it simply makes no sense. Plasmic Physics (talk) 00:27, 20 November 2010 (UTC)

A gun that shoots pure entropy would be like a gun that shoots pure temperature, or pure color, or pure beauty. Abstract concepts can't be shot from a gun. Looie496 (talk) 00:46, 20 November 2010 (UTC)

I dare say you haven't had much practice. --Trovatore (talk) 11:12, 20 November 2010 (UTC)

If you say it that way, it actually sounds comical, like something you would find in Hitchiker's Guide to the Galaxy. An abstract concept gun compoared to the point of view gun. Plasmic Physics (talk) 01:10, 20 November 2010 (UTC)

But again, in all seriousness, all weapons (I've been trying in vain to think of an exception) serve to increase entropy at the local level in their targets. The entire goal of a weapon is to disrupt all of that important and necessary order that is necessary for living organisms or buildings or technologies to stay alive or stay standing or keep functioning. Humans need entropy to be pretty low in order to survive — move their stomach a few inches in the wrong direction, or push down on their neck with a few pounds of force in a small enough time span, and their bodies quickly become disordered, jumbled, rotting, etc. The force of the weapon's ability to increase entropy is usually limited by the ability to keep entropy low — through, say, having a rigid target, or by having a target that will too readily become disordered and dissipate the energy of the entropy-raising projectile (e.g. earthworks or the ceramics used in bullet-proof vests). Entropy change can certainly be a seen as a way to look at how weapons work, but it's a secondary characteristic. --Mr.98 (talk) 14:15, 20 November 2010 (UTC)

Of course, energy isn't technically matter either, unless you consider energy being carried in photons and packets. Maybe it would qualify if you had some type of antimatter ray gun that would cause small areas to undergo 100% entropic destruction efficiency. Otherwise, a psychological weapon such as staring could increase abstract entropy at a distance for this very abstract concept. ~AH1^(TCU) 03:33, 21 November 2010 (UTC)

Parts of the body where cancer *can't* happen?

Are there any human organs or tissues that haven't been associated with any known cases of cancer? NeonMerlin 00:48, 20 November 2010 (UTC)

Hair, fingernails and toenails. Maybe teeth? HiLo48 (talk) 01:33, 20 November 2010 (UTC)

To explain HiLo48's answer, cancer is a disease of cell division; any part of the body where cells can divide (and all living cells can divide) could experience cancer. Hair and fingernails have no living tissue, so they cannot have cancer. --Jayron32 01:38, 20 November 2010 (UTC)

Cancer can occur within teeth, by the way. The enamel isn't living but inside you have the pulp which is highly vascularised. Regards, --—Cyclonenim | Chat  16:53, 21 November 2010 (UTC)

Somewhere there should be a table of the frequency of occurrence of cancer in various organs and tissues. It is common to read of cancers of the skin, breast, lung, liver, lymph node, brain, bladder, prostate, pancreas, tongue and cervix. Some of these have specific tests one is supposed to undergo at certain ages, and some even have highly publicized fundraising and awareness-creating events. I have rarely if ever read of cancer of the heart, artery, vein, fat, muscle, sclera, iris, retina, optic nerve, inner ear, cartiledge, appendix, uvula, penis, tonsil, gall bladder or kidney, though I am confident some cases occur. Edison (talk) 20:30, 22 November 2010 (UTC)

Retinal cancer is most common as retinoblastoma and there are about 40-50 cases in the UK per year (which is pretty rare!). Cancer of the kidney isn't that rare, and cancers of the blood system (i.e. in veins and arteries) can be caused by metastatis into the blood and then into the endothelial lining. Regards, --—Cyclonenim | Chat  14:39, 23 November 2010 (UTC)

The cancers which metastasize into the circulatory system are more likely to start in the lungs or breasts than in, say, the heart muscle. Why? Isn't cancer more likely to start in the breast than, say, the buttock, the elbow, or the shoulder? The skin gets melanomas or some other cancer when exposed to UV for long periods, just as the lung gets cancer from tobacco. Is there a specific irritant to the breast or testes or bladder or prostate which promotes genesis of cancer, which the elbow or buttock is spared? Where is there a tabulation of cancer incidence of different tissues or organs? Edison (talk) 15:08, 23 November 2010 (UTC)

The thing here is that we have cancers that are more common because of prevelent carcinogens happening to affect those areas. We have more respiratory tract cancers than other sorts of cancers because of tobacco smoking. Cancer is more likely to start in the breast than the buttocks but that is mostly due to sheer genetics. The genes that cause breast cancer seem to be more suseptible to changes in structure than those coding for other regions, but I don't personally know why that is. This table shows, in the UK, the most common cancers by incidence rate excluding non-melanomic skin cancer. It's important to note that a lot of research is ongoing and not a lot is completed. There may be specific carcinogens affecting things like prostate cancer incidence but they are currently not known. Regards, --—Cyclonenim | Chat  18:31, 23 November 2010 (UTC)

The name of intermolecular forces acting between alkanes

What is the name of intermolecular forces acting between alkanes, especially large alkanes such as decane? I think they are a special case of van der Waals forces, but van der Waals forces also include H-bonding and dipole-dipole attraction which are not present in alkanes. 220.253.217.130 (talk) 01:22, 20 November 2010 (UTC)

London dispersion forces. --Jayron32 01:34, 20 November 2010 (UTC)

Note that our van der Waals force article lists the three major subtypes, including London. DMacks (talk) 06:27, 20 November 2010 (UTC)

White Dwarf

How close does a white dwarf have to be to another star to "steal" hydrogen? —Preceding unsigned comment added by 76.161.251.228 (talk) 14:26, 18 November 2010 (UTC)

I don't know what answer to give you, but I can tell you that there is no real cutoff value for the distance. Gravity is responsible for this phenomenon, and it decreases exponentially with radial distance from the white dwarf. You should specify the rate at which mass is gained or lost, and the mass of the white dwarf. Using both these variable, someone can calculate an answer. Plasmic Physics (talk) 03:12, 20 November 2010 (UTC)

Harrumph. Gravity doesn't decrease exponentially with distance. It decreases as the inverse square of the distance. That is, it varies as 1/r², not 1/a^r. --Anonymous, 06:25 UTC, November 20/10.

Sorry, bad mistake, but the rest of what I said still holds. Plasmic Physics (talk) 06:32, 20 November 2010 (UTC)

That would be the Roche limit. It depends on the masses and radii of the white dwarf and the star. I would try the formula given in the subsection about a fluid satellite. --Wrongfilter (talk) 11:18, 20 November 2010 (UTC)

Hmmm ... but the huge difference in densities between the white dwarf and the secondary probably means that the Roche limit is less than the radius of the secondary star, so the stars will collide before the Roche limit is reached. We can get a ballpark upper limit by looking at the period of the cataclysmic variable binaries listed in the Catalog and Atlas of Cataclysmic Variables. Most of these periods are less than 1 day. If the main star has a mass comparable to the Sun, then an orbital period of 1 day means an orbital radius of around 3 million km, or about 4 to 5 times the radius of the Sun. So a ballpark figure is "within 5 solar radii". The exact answer for a given binary will depend on the masses and temperatures of the stars involved, and probably on a lot of more complex factors such as their magnetic fields. Gandalf61 (talk) 11:38, 20 November 2010 (UTC)

Trapping antihydrogen

The antihydrogen was created back in 1995, as the article says, so why to claim that its atoms are now trapped? It's akin to saying that I baked a bread some time ago and now captured its crumbs. —Preceding unsigned comment added by 89.77.156.31 (talk) 09:09, 20 November 2010 (UTC)

Antihydrogen is as stable as hydrogen, but it's hard to keep around because it annihilates on contact with ordinary matter. Thus there's a difference between merely producing it and preventing it from annihilating afterwards. -- BenRG (talk) 09:17, 20 November 2010 (UTC)

I think you have misunderstood the intended meaning of "since 1995" in the antihydrogen article. Each individual atom of antihydrogen only exists for a fraction of second before it is annihilated by contact with "ordinary" matter. The recent breakthrough was to trap atoms of antihydrogen with relatively low energies ("cold" antihydrogen) usaing magnetic fields - but even these atoms could only be kept for one sixth of a second. Antihydrogen atoms are created fresh for each experiment by bombarding a target in a particle accelerator - the antihydrogen atoms that were created back in 1995 are long gone. Gandalf61 (talk) 10:46, 20 November 2010 (UTC)

Initially, only antihydrogen-nuclei could be studied. Without positrons electrons, the nuclei are negatively charged, allowing them to be captured and contained indefinitely within a Penning trap. The trick was to create neutral atoms, a Penning trap is useless at containing neutral atoms. It is this proble that was recently overcame. Plasmic Physics (talk) 12:30, 20 November 2010 (UTC)

Space marines/soldiers?

I remember reading a while back about a Navy or Air Force veteran who wanted to start a U.S. Space Marines or something. He planned to send these five guys into space and said they should practice Tai Chi and Meditation techniques to keep them at peak psychological stamina. Anyone know about this?--Editor510 ^{drop us a line, mate} 12:53, 20 November 2010 (UTC)

I find it unlikely that one would send soldiers to space for any sort of benefit. They could practice Tai Chi and meditation on Earth in quiet rooms if they so desired at much less cost. On top of this, low/zero-gravity is known to affect muscular fitness and with enough time wastage can occur. I don't think it'd be beneficial for soldiers to go to space. Regards, --—Cyclonenim | Chat  15:10, 20 November 2010 (UTC)

Yea, astronauts who spend more than a week or so in space usually can't even walk when they land. They would hardly strike fear into our nations enemies. APL (talk) 21:10, 20 November 2010 (UTC)

You mean like Orbital Drop Shock Troopers? Cool. :] WikiDao ☯ (talk) 15:54, 20 November 2010 (UTC)

Or these space marines? SmartSE (talk) 21:05, 20 November 2010 (UTC)

Very, very expensive on top of everything else, and they'd have to rely on a certain foreign power of uncertain disposition to get them there and back, now that the Space Shuttle is being retired (unless Virgin Galactic expanded its reach considerably). Clarityfiend (talk) 20:28, 20 November 2010 (UTC)

Check out Blue Gemini. It was to be a military version of the space program that would have run parallel to the Nasa Gemini program and served as a build-up to a military run space station. It was canceled because it wasn't cost effective to have two space agencies.

Nowadays, of course, by this time next year USA will have no launch vehicles. We couldn't put soldiers up there if we wanted to! APL (talk) 21:10, 20 November 2010 (UTC)

None of this is it. It was a crazy idea, it was just a concept that some veteran wanted to make real. I think I read about it on Cracked.com? I need to find the relevant Wikipedia article. The men sent up were supposed to be like ambassadors and it was only supposed to be a small team. 'Space Taskforce' might be a name, but I wouldn't swear to it.--Editor510 ^{drop us a line, mate} 23:35, 20 November 2010 (UTC)

There are two articles on Cracked.com about them neither of which mention it. Is there a chance you've mistaken the role of the United States Marine Corps astronauts? They are afterall the only real "space marines". SmartSE (talk) 12:39, 21 November 2010 (UTC)

They're not in space, but check out First Earth Battalion for some hippy-dippy military stuff. --Sean 16:23, 22 November 2010 (UTC)

It was them! Thank you! Unfortunately, I found it out for myself elsewhere before I read this, but I would have been even more grateful if I had come back before. Thanks.--Editor510 ^{drop us a line, mate} 17:14, 27 November 2010 (UTC)

Understanding inflammation

If inflammation is "part of the complex biological response of vascular tissues to harmful stimuli" and, therefore, as I understand it, a positive state during which the body is attempting to heal tissue damage; why are anti-inflammatories, ice, etc. (with hopes of reducing inflammation) prescribed? By consciously reducing inflammation, aren't we really hampering the body's effort to heal the damage? Or is that we are not really attacking the inflammatory process itself but we're actually speeding it up - and therefore, it goes back to a non-inflammatory state faster, "reducing" the inflammation? --Belchman (talk) 13:56, 20 November 2010 (UTC)

Surprise: Scientists discover that inflammation helps to heal wounds. So I think this all means that: if you want to 'recover' fast from say a marathon, then a 'cool' but not cold bath gets you back to normal fast, but for training perposes, let nature take it's course. --Aspro (talk) 16:06, 20 November 2010 (UTC)

Thanks to anyone that helps me with this question, but I'm particularly interested in a physician's opinion if possible - I hope that non-physicians understand this. --Belchman (talk) 17:06, 20 November 2010 (UTC)

Anti-inflammatory drugs do actually inhibit the inflammatory response, and ice causes local vasoconstriction which impairs the influx of inflammtory mediators. So yes, you're absolutely right in your first hypothesis – we really are putting a damper on the body's natural response to damage. That's why most of the time you're better off just taking a heaped spoonful of Harden-Up instead of reaching for the Brufen every time you get a niggle. The reason we do prescribe anti-inflammatories in some cases is because sometimes the inflammatory repsonse can be worse than the initial injury. Conditions like osteoarthritis and rheumatoid arthritis, and some severe traumas fit this description. I'd say most people use anti-inflammatories just to take the edge off the pain of inflammation, so the reparative effect is still there, just diminished slightly, so the affected person can get on with their lives to some degree. Mattopaedia ^{Say G'Day!} 10:35, 22 November 2010 (UTC)

Having just recovered from an acute attack I can say gout is another. Nil Einne (talk) 15:52, 22 November 2010 (UTC)

Indeed. We could make a really big list, but we won't, right? Mattopaedia ^{Say G'Day!} 22:09, 22 November 2010 (UTC)

Like other immune responses, inflammation may require treatment if the body's reaction spirals out of control such that it interferes with normal activity (see Functio laesa). Fever is the classic example there, where moderate fevers have a variety of host defense effects, but too high or prolonged a fever can put you in a difficult place. Matt Deres (talk) 04:00, 23 November 2010 (UTC)

Thank you all, those answers were excellent. --Belchman (talk) 22:30, 23 November 2010 (UTC)

Of note, you're not going to get a physician's answer here. Wikipedia does not give out medical advice. We're all just volunteers providing information we've found through research. — The Hand That Feeds You:^Bite 15:56, 24 November 2010 (UTC)

Formal classification of fallacies

What are all the formal fallacies the second respondent at <a href="http://theboard.byu.edu/questions/60673/">this</a> site (the one who tries to reverse the Galilean experience into a defense of religion) commits? I was looking at List of fallacies and "appeal to authority" seems to fit the way he's able to determine for himself that "if I feel good after doing X, X must be a good thing." which itself fits under "correlation does not imply causation." Any other/better analyses? Thanks. 76.27.175.80 (talk) 14:04, 20 November 2010 (UTC)

That's sort of a long post at that link. Can you help narrow down your question by quoting from it exactly where you see the fallacy you are asking about being applied? WikiDao ☯ (talk) 14:46, 20 November 2010 (UTC)

When he or she says "truth is truth" (which I take as the "Galilean" section — Earth and sun and etc.) it's just tautology. The general argument is axiomatic with a tiny bit of "it makes me happy" thrown into it. But I don't think he or she is committing a strict logical fallacy here. It's just an appeal to faith. He or she is pretty self-consciously aware that this does not constitute scientific evidence and would not be compelling to skeptics. --Mr.98 (talk) 15:03, 20 November 2010 (UTC)

The "if I feel good after doing X, X must be a good thing" line of reasoning sounds like an argumentum ad consequentiam.

The poster's invocation (at the link given in the OQ) of "I plant the seed and take care of it and it grows" as applying to LDS Church (ie. that it exists as a "major" religion these days; therefore, it must be divinely favored; therefore, God exists and the LDS Church is good and true...) involves Retrospective determinism (and, historically, also involved a certain degree of argumentum ad baculum from what I understand). There are many more fallacies of reasoning in that post. I'd say Wishful thinking may well pertain, too. WikiDao ☯ (talk) 17:48, 20 November 2010 (UTC)

Here are a few more fallacies being used, to add to the ones already identified above:

The first two paragraphs can be paraphrased as "I'm a scientist, and I know that God exists", which is an appeal to accomplishment.

The fourth paragraph says (with minor paraphrasing) that "the evidence of faith's creation is a confirmation to the individual that comes directly from God, therefore the proof of faith is infinitely more powerful than the logical demonstration of scientific data". That's basically begging the question, which is closely related to circular reasoning. God's existence is the main conclusion to be proven, so it can't logically be used as part of a premise.

The fifth paragraph says (verbatim) "as far as it being verifiable, you can receive a similar witness of the Holy Ghost every time you read the Book of Mormon". The logical content of that statement can be reexpressed as the indicative conditional "if you read the Book of Mormon, then you will receive a witness of the Holy Ghost". Unlike much of the surrounding material, that indicative conditional is actually a falsifiable premise, which is a good thing. However, when I do the experiment, I find that that premise is false. I.e., when I read the Book of Mormon, I just perceive the thing as being utter horseshit, rather than having the sensation that I'm receiving some kind of divine evidence of the Holy Ghost. Not logically supporting a very questionable premise like that amounts to an ipse-dixitism, which is related to a bare assertion fallacy. Red Act (talk) 22:28, 20 November 2010 (UTC)

Thanks, and something tells me if you told him you didn't hear a "yes" on that last indicative conditional, he'd respond that it's because you didn't read enough or pray hard enough :) 76.27.175.80 (talk) 03:52, 21 November 2010 (UTC)

Mental disorders

Is bipolar disorder a real disorder or are some people just moody? Is ADD a real disorder or are some people just easily distracted? Is narcissistic personality disorder a real disorder or are some people just full of themselves? --124.254.77.148 (talk) 14:16, 20 November 2010 (UTC)

Yes. just change all your or's to and's and you're right:) WikiDao ☯ (talk) 14:27, 20 November 2010 (UTC)

I've known many people who were classic bipolar, and it goes far, far beyond "moody." They swing between completely manic and completely paralyzed depressed. It's clearly some kind of major chemical imbalance and it often completely inhibits their ability to be effective people. I can be "moody" in the sense that sometimes I'm more effective or elevated and sometimes I'm grumpy or sad. But that's not what bipolar is. Now every spectrum disorder (like bipolar, or ADD) has some shades of being similar, at its mildest levels, with what we define as "normal" variation. But when it crosses into the extremes it is pretty apparently the sort of thing which conflicts with how people function and is largely out of their control. That's usually when we class those kinds of extremes as being "disorders". --Mr.98 (talk) 15:07, 20 November 2010 (UTC)

There is some controversy over the existence of several classified mental disorders, but generally bipolar is characterized by mood states that are persistant—ie. they are nearly impossible to simply "snap out" of, likewise for major depression and various forms of psychosis. ~AH1^(TCU) 00:54, 21 November 2010 (UTC)

Vehicle identification

Hello fellows!

Does anybody know who is the manufucturer of these two vehicles and which type is it.

• File:CU-Juggernaut crane on a flatbed railroad car.JPEG
• File:Wheeled bulldozer in 1973.JPEG

Thanks for helping. Cheers, High Contrast (talk) 16:41, 20 November 2010 (UTC)

You've also asked at the Miscellaneous desk where I think this question is more appropriate. I suggest the answers should go there. Franamax (talk) 17:03, 20 November 2010 (UTC)

For the first, the clue is in the name - I searched for "juggernaut tracked vehicle" and found this site, number 32 is a similar vehicle which is a Thiokol juggernaut. Then I searched for "thiokol jugernaut", found this which has a link to this which shows it is a Thiokol Juggernaut 6T that has been adapted with a drill rig. The bulldozer is a lot more difficult though, I'll have a hunt, but if nobody here can help this forum might be the place to ask. SmartSE (talk) 20:49, 20 November 2010 (UTC)

I've surprised myself, but I think it is a Caterpillar 830M, based on this listing on craigs list and this book which says they were made for the military, which obviously fits with the source and the timing. Here's a better picture of one in another book as well. SmartSE (talk) 21:02, 20 November 2010 (UTC)

Thanks for helping! Cheers, High Contrast (talk) 08:53, 23 November 2010 (UTC)

Is bobbing your head to music an instinctual act or a learned one?

Thanks--72.178.134.134 (talk) 17:22, 20 November 2010 (UTC)

Definitely learnt. People in the tropics obviously got the idea from watching their parrots. [1] --Aspro (talk) 17:40, 20 November 2010 (UTC)

Aspro's answer was probably a joke. I've seen babies do it, so it's probably instinctual. Ariel. (talk) 23:33, 20 November 2010 (UTC)

A source to back up Ariel's point, see the procedure of experiment two. Quite why this should be instinctive is another matter... SmartSE (talk) 14:46, 21 November 2010 (UTC)

A recent BBC news article reported a study that showed chimps using head gestures (up-down and sideways) as humans do. Imagine Reason (talk) 19:24, 22 November 2010 (UTC)

Composting cooked vegetable matter

I've often seen it said that cooked veg shouldn't be added to compost heaps. Why is this? Thanks. DuncanHill (talk) 17:32, 20 November 2010 (UTC)

It might be as simple as: cooked veg is sterilised veg and has most of its low temperature enzymes (those that would cause natural lysis) get inactivated. Thus, it would be an ideal culture medium for anaerobic bacteria. Its the thermophilic anaerobics what course smelly drains etc., and there is plenty of heat in a good compost heap. The solution is not to have the heap directly outside kitchen window, but in the traditional place at bottom of the garden. Bones and things in my experience don't cause any problem either. Spread out each layer, rather than dump it on, so that the air can get to it. Any vermin issues gets more than offset by having to buy less cat food.--Aspro (talk) 17:54, 20 November 2010 (UTC)

Thanks, that makes sense. I suspect that mixed with sufficient raw trimmings, peelings and garden waste it should be fine. DuncanHill (talk) 20:11, 20 November 2010 (UTC)

Looking at the sites that give this advice not to use cook food, they appear to be for these piddling little green composting drums. They also don't advise wood ash. Thinking back to when I kept two large compost heaps on the go (about 2 foot square a piece), I would put anything organic on them, even chicken heads and their eviscerate, dead rats, pizza shaped roadkill etc., by putting down first, a layer of dirt and then a bit of wood ash over the top of the carcass and offal. The lyle or potassium hydroxide in it, helped I guess, to brake down the tissue in an alkali environment and the soil bacteria stopped any smells arising. Certainly don't remember any smells. If it was organic it when on. What I had left after sieving into the wheel barrow (bones, woody bits and so on), went back on to the new heap for a second pass. Garden waste has plenty of bulk but if one is just using kitchen scraps, then that might need more careful layering as you say. --Aspro (talk) 21:01, 20 November 2010 (UTC)

You should definitely not put everything organic in the compost, many organic compounds are highly toxic. Some examples of organic things that should not be added to the compost are used motor oil, most types of plastics, left over medication and many chemical weapons. --Gr8xoz (talk) 22:11, 20 November 2010 (UTC)

The Kim & Bin Laden Chemical Recycling Company Ltd will dispose of any unwanted chemical weapons at very reasonable rates, I understand.

Organic matter...You were saying?....--Aspro (talk) 22:16, 20 November 2010 (UTC)

We are talking about “garden” compost heaps. Why bring in these other things? Which 'chemical weapons' do you keep at home? The US has spent millions on weapon composting techniques : Bacterial detoxification of organophosphate nerve agents . You might show a light on upstairs but I ask myself “is anybody home?!!”--Aspro (talk) 22:30, 20 November 2010 (UTC)

If you're using a small compost bin and want to mix the cooked veg with more stuff, you can always add newspaper, tissues, kitchen wipes and cardboard. If the bin starts to smell put plenty of ripped up newspaper in. The one thing I would recommend keeping out is citrus peel, because it does make the compost smell nasty as it rots. Itsmejudith (talk) 00:06, 21 November 2010 (UTC)

I believe Gr8xoz is making a point about the use of the word "organic". In certain contexts, "organic" simply means "containing carbon". (e.g. organic chemistry) - by that definition, motor oil and chemical weapons count as "organic". On the other hand "organic" in the context of organic farming is a too-narrow restriction on compostables - most conventionally grown fruits and vegetables are perfectly fine for the compost. That said, Aspro is correct in assuming that the context reasonably implies "organic matter". -- 174.24.198.158 (talk) 19:51, 21 November 2010 (UTC)

Excimer lamp

Hello, what is the overall luminous efficacy (lm/W) of an excimer lamp?, ideal black-body radiator at 7000 K has 49 lm/w, so 180 lm/w like some stupid friend of mine pretends that a self invented excimer lamp should produce would be total trashtalk (his 5w selfinvented excimer lamp produces 900 lm)?TY DST —Preceding unsigned comment added by 86.127.164.33 (talk) 19:10, 20 November 2010 (UTC)

See Luminous efficacy, 49 lm/W seems to be wrong a ideal black-body radiator at 7000 K has 95 lm/W, the theoretical maximum is 683 lm/W for an ideal source of 555 nm yelow light. Low pressure Sodium-vapor lamp gives up to 200 lm/W. I do not know much about Excimer lamps but 180 lm/W should not be unrealistic. --Gr8xoz (talk) 22:00, 20 November 2010 (UTC)

Yellow? 555 nm is usually considered green. I agree 180 lm/W seems rather high particularly if we're talking about white light. Even the best commercial cool white LEDs only produce ~140-150 lumens/watt under optimal conditions for example (and the best I've heard from research is 200 lm/W). Nil Einne (talk) 06:44, 21 November 2010 (UTC)

I see no reason to assume that we talk about white light, but of course 180 lm/W white light is very good and unlikely. Excimer lamps seems to be mostly monochromatic and often in the UV-range, obviously the luminous efficacy is 0 lm/W in that case. I was assuming a monochromatic light in the visible range, and if the claimed 180 lm/W is correct it. will be close to 555 nm. Sorry about the mix-up about colours, I assumed that low pressure Sodium-vapor lamps where close enough to 555 nm that they should have the same colour. Low pressure Sodium-vapor lamps emits 589.3 nm which is yelow. An approximation of the colours are 555 nm and 589.3 nm --Gr8xoz (talk) 12:02, 21 November 2010 (UTC)

You may be right, I don't really know what an excimer lamp is, I was just surprised the OPs friend would be that excited about a non-white light (although there are obviously some applications like novelty lighting, advertising, traffic lights, aquarium lighting etc depending on the precise colour) as at the moment most interest is generally in white lights. The differences between wavelengths at that area can be rather major, I myself wasn't that aware until I developed an interest in LEDs File:Linear visible spectrum.svg Nil Einne (talk) 13:55, 21 November 2010 (UTC)

Scott toilet tissue ad touts no inner tube.

But can't that cardboard be recycled? Less waste is good, I suppose, but I'm still curious. Thanks. Imagine Reason (talk) 20:09, 20 November 2010 (UTC)

So what is the question? Yes a cardboard inner tube can (but may not) be recycled. However a cardboard tube costs money for the producer - a direct overhead. If they have a way of winding paper without the core then once they've the right machines it should cost them less AND they can advertise the cost saving to them as an environmental benefit (and perhaps charge more for it). -- SGBailey (talk) 21:28, 20 November 2010 (UTC)

A company engaged in greenwashing? No wai! DMacks (talk) 21:34, 20 November 2010 (UTC)

That's not greenwashing, since it does actually reduce resources. My rule of thumb: If it benefits the environment, but costs more, then it's usually greenwashing. (If things cost more then they use more resources, which means they don't actually benefit the environment. There are some exceptions, but it's a good rule of thumb.) Ariel. (talk) 23:52, 20 November 2010 (UTC)

There can be some actual green, doesn't mean they get off Scott free (sorry!) on ulterior/"not the whole truth" concerns. Googling various non-extremist news sources and commentaries pretty commonly uses this term for this product, but is fairly split about whether it's "bad" or not--our article on the term doesn't say that there can't be an actual green benefit. They've got a product that costs less to manufacture but they're maybe even going to charge me more for the privlege of their improved process? Who profits more here, company or Nature? The roller is only a small part of the whole product, and the paper itself is only about half post-consumer recycled it appears, so seems like a small improvement (with loud crowing) even if there are much larger strides that could be made. I think I'm going to drop this line of conversation here (I'm not the enviro-wacko this paragaph might make me sound like:) lest it devolve into soapboxing one way or the other. DMacks (talk) 00:14, 21 November 2010 (UTC)

I'm not sure about that rule of thumb. Some things benefit the environment by not using some cheap but horrible substance. (Mercury, CFCs, DDT, what have you.) APL (talk) 20:22, 21 November 2010 (UTC)

I did say there were exceptions, and those are exactly it (and pollution in general). But most of the time when you are going to buy something you not faced with such choices. Ariel. (talk) 21:53, 21 November 2010 (UTC)

Anti matter

Why is antimatter important? I understand trying to understand and produce antimatter is part of understanding what makes up the universe and how it works, but do some people think it would be useful for a new class of weapons, or energy production, or could it affect how we travel or build things. Would it fundamentally change our view of how the universe is structured? Laura —Preceding unsigned comment added by 41.225.41.4 (talk) 21:13, 20 November 2010 (UTC)

None of the above, which does not mean it doesn't have any uses. For instance, anti-matter is produced inside our bodies in a pet scan machine in order to create a image for medical purposes. 76.123.74.93 (talk) 21:48, 20 November 2010 (UTC)

The answer to the question "would it fundamentally change our view of how the universe is structured?" isn't really knowable with complete certainty in advance. Some of the experiments scientists hope to do with antimatter include verifying the gravitational interaction of antimatter and testing CPT symmetry. Unexpected results to either of those tests could in principle have major theoretical ramifications. Drastically unexpected results do occur in physics experiments from time to time which lead to major theoretical breakthroughs (although not very frequently). Red Act (talk) 23:04, 20 November 2010 (UTC)

True, besides, antimatter has already fundamentally changed our view of the universe when it was first discovered decades ago. 76.123.74.93 (talk) 23:12, 20 November 2010 (UTC)

You might be able to, at some point far in the future, to assemble enough antimatter to make an antimatter bomb but if you had the technology to do that it would probably be easier to just make nuclear fission weapons. It would surely be more unwieldy than the mass/energy ratio would imply, for the same reason nuclear weapons are more wieldy than their fissile cores (it would take some considerable apparatus to keep such a weapon from blowing up before you wanted it to). You can't use antimatter as an energy source as far as I know because it takes more energy to produce it than you'd get as a result, at least with current methods. Any potential technological applications are a long way off as far as anyone can currently guess. --Mr.98 (talk) 23:49, 20 November 2010 (UTC)

The main value of antimatter lies in the relatively distant future. It is the most efficient possible way to store energy. If you have equal masses of ordinary matter and antimatter, they can be combined to transform the entire total mass into energy. Theoretically there is no way to store the same amount of energy with less mass. Thus antimatter would be the ultimate fuel for something like a starship. Looie496 (talk) 00:18, 21 November 2010 (UTC)

See W and Z bosons, cosmic inflation, baryogenesis, antineutrino, Kardashev scale#Energy development, antimatter rocket, antimatter tests of Lorentz violation, Higgs boson, black hole starship and Large Hadron Collider. ~AH1^(TCU) 00:40, 21 November 2010 (UTC)

http://memory-alpha.org/wiki/Matter-antimatter_reaction_assembly —Preceding unsigned comment added by 142.244.236.20 (talk) 22:10, 21 November 2010 (UTC)

The answer is mostly Science Fiction. (Star Trek probably has a lot to answer for in this regard.)

The idea that appeals to science fiction writers is the idea that only a small amount of antimatter could produce a phenomenal amount of energy. So if you had a super easy way of storing it, you could a bomb that fits in your pocket but has more power than the Hiroshima bomb. Or you could fuel your car forever on a microscopic amount of fuel. And of course, A serious obstacle in spaceship design is that the fuel is so heavy. Antimatter fuel could go a long way towards solving that.

Of course, for a science fiction writer it's easy enough just to say that we've got a large amount of antimatter. In real life no one's even got a good idea how you would even try to make that much of the stuff. APL (talk) 00:48, 21 November 2010 (UTC)

Why not just make a gigantic solar-powered anti-mater factory in low-solar orbit and have all of our ships fuel up there? 142.244.236.20 (talk) 23:27, 21 November 2010 (UTC)

Cost I expect. Googlemeister (talk) 17:00, 22 November 2010 (UTC)

It is important because it is a fundemental truth about the universe, about which we do not know everything there is to know. There is no greater reason to be human than to learn. --Jayron32 02:25, 21 November 2010 (UTC)

And a lot of useful applications for discoveries appeared long after they were first found. 142.244.236.20 (talk) 23:27, 21 November 2010 (UTC)

Rootstocks

Anyone know for sure if "semi vigorous" is more or less vigorous than "moderate vigour". I am comparing Montclaire with St Julien rootstocks and the catalogues are not consistent about which will grow a bigger tree. --BozMo talk 21:43, 20 November 2010 (UTC)

There may not be any industry standard; each grower or supplier may use its own terminology. --Jayron32 02:23, 21 November 2010 (UTC)

Tin iodide coloration

Why are the tin iodides colored? Is it impurities or the arrangement of the molecules? --Chemicalinterest (talk) 22:20, 20 November 2010 (UTC)

Neither. It is due to a ligand-to-metal charge-transfer transition (or LMCT transition for short). In very rough terms, you can think of it as an electron hopping from an iodide ion to a tin ion under the influence of visible light; it doesn't actually go "all the way", because there's a big covalent character to the bond. The effect is greatest for iodides because the ionization energy of the iodide ion is much less than for bormides or chlorides: so iodides are always more like to be coloured, and will always be more strongly coloured and at shades nearer to red, than bromides or chlorides. Physchim62 (talk) 23:29, 20 November 2010 (UTC)

Our charge-transfer complex article is in pretty good shape I think. DMacks (talk) 00:00, 21 November 2010 (UTC)