The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
If one has a molecule which has coordinate covalent bonds - that is, both electrons for the bond are provided by one atom - how is hybridization calculated? For the atom providing the electrons, I believe the bond counts as an unshared pair of electrons, but does it affect the hybridization of the receiving atom? If so, how? As an example: I believe sulfuric acid, H2SO4, has two coordinate covalent bonds between the central sulfur and two of the oxygens. How would one calculate the hybridization for the oxygens? FlamingSilmaril (talk) 00:21, 17 July 2008 (UTC)[reply]
I believe once the bond has been formed, it is treated like any other covalent bond. It doesn't matter where the electrons came from; they are shared between the atoms the same as if it is a coordinate covalent bond, a "normal" bond, or from some sort of electrochemistry. As the article says, it's an "artificial" distinction. --Bennybp (talk) 00:54, 17 July 2008 (UTC)[reply]
(Hopefully someone can correct me if I'm wrong; it's been years since I've done this). For the oxygens with a double bond to the sulfur, the hybridization would be sp2 - 2 hybrid orbitals containing the 2 loan lone pairs, and one containing the σ bond to the sulfur. The leftover p orbital is used in the double (π) bond. For the oxygens containing to the H group, the hybridization is sp3 - one containing the bond to the sulfur, one containing the bond to the hydrogen, and two containing lone pairs. --Bennybp (talk) 01:39, 17 July 2008 (UTC)[reply]
Okay, that makes sense. But are the bonds double (in which case sulfur would need an expanded octet) or coordinate covalent? In my high school chem class they told us it would be coordinate covalent, but are they dumbing it down for simplified chem 1 purposes? And if it's coordinate covalent, does that change things? Thanks for your help. FlamingSilmaril (talk) 01:55, 17 July 2008 (UTC)[reply]
Hybridization schemes involving d orbitals are also possible. They are important for elements in the third and succeeding rows of the periodic table. Although the elements of the third row do not possess occupied 3d orbitals in their ground electronic configurations, the 3d orbitals of phosphorus, sulphur and chlorine are low enough in energy that promoted configurations involving the 3d orbitals may be reasonably postulated to account for the binding in compounds of these elements. One consequence of the "availability" of the 3d orbitals is that there are many exceptions to the octet rule in compounds of the third row elements
That may still be debatable. (or no longer believed true). You probably don't have to worry about that anyway - d orbital contribution may only be partial.
The hybridisation on O is difficult - for the OH oxygens you can expect sp3 (as in water), for the =O oxygens you might expect that the double bond be provided by a p orbital - this means that the remainder of the orbitals can form sp2 or (sp and p).
It's worth noting that the S=O bond can be quite polar eg S+-O- ; negative charge on the oxygen tends to favour s or sp orbitals (I think)
(eg compare the stabilities of CH3-, CH2=CH- and CH=CH- anions -also a first row element).
The SO bonds are double, the SOH bonds are single.
The S can be considered to have and expanded octet.
The S=O bonds can be considered to be dative from S to O or as a single bond sharing one electron each from S and O with O supplying a further dative bonding pair to S forming the double bond and expanding the S octet.
1. OH
|
-O-S2+-O-
|
OH
2. OH
|
O=S=O
|
OH
3. O
↑
HO-S-OH
↓
O
1,2 and 3 are all valid structures, 1 shows a polar covalent bond, 2 shows the double bonds , 3 shows the dative bonding form. NOTE only in 3. has sulphur not expanded its octet.
1 is unlikely because of the +2 charge, 2 is more likely because the S=O bonds are shown to be quite strong, for that reason the singly bonded form 3 is unlikely.
Ah, see the picture to the right. You are correct - sulfur contains an expanded octet - two double bonds, two single bonds, for a grand total of 12 valence electrons. Perhaps your teacher misspoke or was incorrect in calling the bonds "coordinate covalent" (or dative, the term I had learned). A double bond is of course a type of bond. A coordinate covalent/dative bond is more of a description of how that bond got there. Once the bond is formed, it's more or less irrelevant how those electrons came to be shared. Sulfuric acid structure--Bennybp (talk) 02:56, 17 July 2008 (UTC)[reply]
Quick note about the hybridized d oribitals mentioned above - you are also correct. In some there can be hybridized sp3d, sp3d2, etc, in some compounds. In this case, who knows. Maybe I'll rummage through my inorganic book tonight. I'm just thankful he/she didn't ask what the hybridization was on sulfur. Yet. :) --66.66.215.73 (talk) 03:28, 17 July 2008 (UTC)[reply]
(unindent) Thanks to everybody who has contributed to the discussion. I do have one question remaining: the article on thiosulfuric acid has the atoms arranged in a cross structure around a sulfur. An AP Chem book that my teacher used said that it is arranged in a straight line: H-O-S-O-S-O-H. It said this was more stable, because it was slightly more symmetrical. A quick glance however, does not show this structure anywhere on the internet. Can anybody shed some light on this? FlamingSilmaril (talk) 22:27, 17 July 2008 (UTC)[reply]
Your book may be wrong, or someone misinterpreted (what book is it?). The structure you gave (H-O-S-O-S-O-H) is 1.) Not linear. 2.) Not symmetric (well, maybe one rotational axis through the center oxygen). 3.) Not thiosulfuric acid. And 4.) Doesn't appear to exist. (The structure was evaluated with ChemSketch,and named "dihydroxydithioxane", which gets zero hits on google and ChemFinder. --Bennybp (talk) 23:28, 17 July 2008 (UTC)[reply]
I'm sure most of us have heard the stories of human vs. kangaroo boxing matches (which are probably illegal in many parts of the world now) at carnival sideshows in the 19th century. What I'd like to know, is whether a trained boxing kangaroo could beat a skilled human boxer. There are some videos of man/kanagroo fights on YouTube - but they all seem to involve the human fighting half-heartedly or refusing to fight back at all for the purposes of comedy.
So, if a (good) boxer really went all out and genuinely tried to KO the 'roo - and the 'roo was likewise trying to inflict serious damage (both wearing gloves, of couse - this is a civilised sport!), which would be the more likely winner? --Kurt Shaped Box (talk) 01:30, 17 July 2008 (UTC)[reply]
I have witnessed a boxing match between kangaroos. They don't follow rules, and also use their strong hind legs. A kangaroo could out jump a boxer. Scratching with claws is part of their methods too. Graeme Bartlett (talk) 04:59, 17 July 2008 (UTC)[reply]
As regards gloves and civilzed-ness: KSB, do you have the idea that when you put on gloves you do it to protect your opponent? No. You do it to protect your own hands, so you can hit your opponent harder. --Trovatore (talk) 05:09, 17 July 2008 (UTC)[reply]
That's talking about gloves+padding, versus gloves without padding. Gloves without padding still protect your hands. Put a bare-knuckle guy in the ring against a guy with gloves, I'll bet on the guy with gloves. The reason bare-knuckle fights could go 57 rounds or whatever is they just couldn't hit each other that hard. --Trovatore (talk) 17:06, 17 July 2008 (UTC)[reply]
My dad worked in a hospital emergency room for a while, and according to him, bare-knuckle bar fights end in either of two ways: (1) the guy throwing the first punch is strong, and breaks his own hand and his opponent's jaw, or (2) the guy isn't so strong, and only breaks his own hand. In either case, punching someone in the jaw with your bare hands is not a good idea. --Carnildo (talk) 20:48, 17 July 2008 (UTC)[reply]
AFAIK, if you break your hand when punching someone, it's usually down to bad technique. For some reason, when untrained people punch, they tend to connect with the fourth and fifth knuckles. Not that I'm a scrapper - but I think the trick is to strike with the second and third, with a straight wrist behind. --Kurt Shaped Box (talk) 22:57, 17 July 2008 (UTC)[reply]
Odd. The claim is that half the padding had been removed from the gloves and that that allowed Resto (who is referred to as "soft-hitting") to beat the good guy half to death (or, if we ignore the DUI as the article does, all the way). But boxing gloves are much more padded than those used in MMA - even half the padding would leave them bulkier than a UFC fighter's gloves. Lewis and Resto are rightly demonized, but the key element here was the incompetent referee who apparently didn't feel the need to check the fighter's equipment or stop a bout that had obviously become a slaughter. Matt Deres (talk) 10:53, 17 July 2008 (UTC)[reply]
I don't really know much about the UFC - but does a typical bout of theirs involve 10x3min rounds of mostly punching someone in and around the face? I thought that it was more of a grappling-based sport? The Collins-Resto fight is on YouTube in its entirity, btw - it doesn't actually look massively uneven until the last three rounds or so. Even then, it was only in the final round that Collins was struggling to stay on his feet. The damage inflicted was cumulative. --Kurt Shaped Box (talk) 15:04, 17 July 2008 (UTC)[reply]
A typical bout is 3x5 minutes, but a title match is 5x5 minutes. While they don't experience the sheer number of punches to the face that a boxer would get, they also get to enjoy kicks, knees, and forearms to the head. I stopped watching boxing as I got into watching MMA style events; while that was mostly driven by the (IMO) more exciting style of contest, I also preferred the sportsmanship and style of refereeing. Maybe it's gotten better over the last decade, but when I was watching boxing it seemed that the refs were doing everything in their power to allow the superior fighter the chance to KO his opponent, rather than simply stopping the fight (as a TKO) when it became obvious that the match had really already been decided. Not having been pummelled myself (!), I tend to agree with Bas Rutten that a quick finish to a fight is much better for the health of the fighters than a prolonged battle with standing counts and more frequent breaks between rounds. In MMA, the referee (or designated other) also inspects the equipment immediately prior to the bout to make sure everything is up to spec. Matt Deres (talk) 16:37, 17 July 2008 (UTC)[reply]
Concentration of biotin in egg yolk.
On a number of websites I've read that despite egg whites containing a substance that removes biotin from the body, egg yolks contain so much biotin to make these effects unimportant. I have however been unable to come up with a source for this -- Wikipedia's own article on biotin mentions that egg yolk contains biotin, but does not reference a source that I can see.
Another Wikipedia article (http://en.wikipedia.org/wiki/Tamago_kake_gohan) states that "Eggs contain many nutrients and protein which are denatured when cooked; therefore it is thought that eating them raw maximises the beneficial effects of these nutrients. The egg yolk contains more than enough levels of biotin to compensate for the high levels of avidin in raw egg white, which binds to the B-vitamin biotin, preventing their absorption and potentially causing a deficiency if the yolk is not consumed with the white." The source it sites for this is a pdf of a letter about, amongst other things, whether wolves should be classed as dogs, and it doesn't exactly inspire confidence in the claim. I'm just looking for a source that gives some exact figures...
Additionally, there is often a claim made that salmonella contamination in eggs only comes about if the chicken is ill, and thus if you buy organic or free range eggs then it is less likely to be infected with salmonella. I have been unable to find a source for this claim either.
After searching on Google, I found [1], [2], and [3], all of which claim there is insufficient avidin in an egg to bind all of the egg's biotin. However, according to this paper, "The yolk of an egg is rich in biotin, but the white usually contains more than enough avidin to inactivate the yolk biotin."
On the matter of salmonella, the U.K. Food Standards Agency found no statistically significant correlation between production type and incidence (see [4]).
Just a historical note: the discovery of avidin/biotin binding and its effects upon the body was by observing a strange ailment affecting a number of athletes who had only one thing in common: they all had been consuming a number of raw eggs (not just the whites, but whole eggs) for a period of at least several weeks. The ailment turned out to be biotin deficiency caused by the sequestration of the vitamin by the avidin in the raw egg. – ClockworkSoul18:07, 17 July 2008 (UTC)[reply]
Litmus paper contains a variety of indicator dyes. The reaction that takes place is a simple acid-base proton (or hydroxide)exchange of the form HIn -> H+ + In-. Indicators are special in that when they lose or gain protons, the absorptive properties of the molecule as a whole are changed. The Phenolphthalein article has some good structures that might help you understand how the conjugated system in the molecule is effected by pH change. --Shaggorama (talk) 04:31, 17 July 2008 (UTC)[reply]
Fixed your confusing typo. --Anon, 05:34 UTC, July 17.
Dream length
What is the average length of a dream? Doing a quick google search gives me results ranging from dreams lasting a split second to experiencing dreams in real time. --Metalcore424 (talk) 09:17, 17 July 2008 (UTC)[reply]
I don't think today it can reliably be measured. In this case measurement of the system drastically affects what we are trying to measure, which would lead to unscientific data and results. Mac Davis (talk) 00:04, 18 July 2008 (UTC)[reply]
Not only that, but you have the problem of what defines a dream; I have had one right after the other, and I would think there was no space in between them, though I'll admit there could have been and I'd never know it. If they can come one after the other, why does your brain change...well..plots? Hmmm, maybe reading the article will help me some witht hat one.209.244.30.221 (talk) 17:35, 20 July 2008 (UTC)[reply]
Given the continental drift over the past 65 million years, it seems as if the impact crater and the caldera were on almost precisely opposite sides of the globe at the time of the event. Are there any theories that somehow make a connection between these two? Frunobulax (talk) 14:45, 17 July 2008 (UTC)[reply]
As dating accuracy gets better, the results repeatedly show that the Deccan Traps predate the Chicxulub crater. It is possible that they happened at the same time - but at this time not widely accepted. If it is proven that they happened at the same time, that will not prove causation. -- kainaw™14:59, 17 July 2008 (UTC)[reply]
They say that the Deccan Traps is the result of a deep mantle plume. These types of plumes happen from time to time all over the world without any special provocation, although the Deccan Traps is a particularly splendid example. Some people have suggested that the impact which caused the nearby Shiva crater may have disturbed the mantle and triggered the plume which formed the Deccan Traps. But really, who knows? PlasticupT/C19:02, 17 July 2008 (UTC)[reply]
You know that funny feeling in your forehead when you place something close to your forehead or inbetween your eyes (especially if it's pointed like a pencil)? How does that work? It seems to activate even if I close my eyes. I never really understood how it works or why. ScienceApe (talk) 15:17, 17 July 2008 (UTC)[reply]
I don't get a funny feeling. Can you describe it in any more detail? I wouldn't recommend putting pointy things too near your eyes though.--Shantavira|feed me15:54, 17 July 2008 (UTC)[reply]
It seems to work more when someone else does it. Have someone point their finger inbetween your eyes or near your forehead. Don't let them touch your head though, but you'll get a funny feeling in your forehead. ScienceApe (talk) 16:00, 17 July 2008 (UTC)[reply]
I definitely know the feeling you mean, but I can't think of what it could be called to search for it here or on google. Fribbler (talk) 16:07, 17 July 2008 (UTC)[reply]
It feels like blood rushing to the area, so maybe it is my body anticipating an impact from the object directly in front of me. PlasticupT/C18:51, 17 July 2008 (UTC)[reply]
I think it is probably due to your eyes trying to see it in your peripheral vision. I don't feel anything nearly at all when I do it with my eyes closed. --98.217.8.46 (talk) 03:52, 18 July 2008 (UTC)[reply]
Since the eyes and brain are very sensitive areas, I suspect the sensation is to warn of a potentially-dangerous object. It still exists when the eyes are closed because when you deliberately induce the feeling with an object, you're well aware of the object's position. When an item unexpectedly gets close to the forehead, I think wind and changes in the amount of light received by the eyes can reveal its location. --Bowlhover (talk) 08:47, 18 July 2008 (UTC)[reply]
I don't know it is the same but my forehead seems much more sensitive to heat or cold than the rest of my face. I can easily tell if there is a hand a couple of inches in front of my forehead with my eyes closed because of the heat. You might feel it as blood rushing to the area. Dmcq (talk) 20:08, 18 July 2008 (UTC)[reply]
ESPAurapersonal bubble its basically latent esp in non-phsycis, and goes to prove that most people are phsycic to a certain degree. It used to happen to me in a hardware store I used to visit, one isle had many habgers for bags of screws and such like and was basically 6 inch rods of metal in an isle 10meters long, 4 feet high and one of there every 10 square cm or so really wierd feeling walking down that isle, i had to avoid it in the end.
Why would a dark brown haired man find about 4 red beard hairs?
I am 27 years old and am a typical Peruvian in terms of aperance. I have dark brown eyes and hair, both my parent as well and all of my grandparents (all Peruvian). Recently I have decided to let my beard grow a little and I ran into a total of 4 red hairs. I have had white hairs on my head, but not on my beard. Is it normal to have a few hairs of a different color? I am a healthy man maybe a little rounder than what I would like. I stand at 5'9 and weigh 176lb, so I don't think malnutrition would be a cause. Why would I have 4 hairs that are of a different color that are not white? —Preceding unsigned comment added by 167.211.65.80 (talk) 15:23, 17 July 2008 (UTC)[reply]
This is a reference desk. It is not a place to list symptoms and ask for a diagnosis. Anyone who answers this question with a proposed diagnosis will be doing you a disservice. Please see a medical expert for a proper diagnosis. -- kainaw™17:19, 17 July 2008 (UTC)[reply]
The OP doesn't seem to be looking for a diagnosis for a medical condition, just a simple explanation about why he might have variation in his hair color. – ClockworkSoul18:00, 17 July 2008 (UTC)[reply]
I agree, calling a question about why hairs come in different colors a request for a medical diagnosis is absolutely absurd. Let's be reasonable here. StuRat (talk) 22:33, 20 July 2008 (UTC)[reply]
Variation in body hair colour in males is not untypical. The genetic basis of red hair is pretty well understood and there is a reported heterozygote effect (having one copy of a specific gene variant) resulting in red beard hair colour in males who do not have red hair on their head. Why one has just occasional red hairs isn't really known, but is probably due to localized perturbation of the melanocytes in those hair follicle, resulting in the production of phaeomelanin rather than eumelanin. Rockpocket19:11, 17 July 2008 (UTC)[reply]
I have dark blonde hair, but a few red hairs in my beard. It was less alarming in my case because my father and brother have red hair, but I don't think it is uncommon, especially when you are young. PlasticupT/C19:05, 17 July 2008 (UTC)[reply]
I know a girl who is complete red-headed/blonde hair colour type except for one black hair on her arm. It doesn't seem that unusual, really. —CycloneNimrodTalk?19:17, 17 July 2008 (UTC)[reply]
I've noticed that some of my eyebrow hairs are a different color and texture. Interestingly, those are the hairs that don't know when to stop growing and must be clipped back. It's like there are two completely different types of hair there. It sounds like you might have this happening with your beard. StuRat (talk) 22:33, 20 July 2008 (UTC)[reply]
Zebra foals
Is the number of foals that a zebra can give birth to in one single go always 1, or have there been cases of multiple births in zebras? Thanks. Leptictidium (mt) 16:21, 17 July 2008 (UTC)[reply]
Upon what criteria do the publishing companies of journals decided to make a particular article free-access? How does it benefit them. Just a curiosity. Thanks in advance. —KetanPanchaltaLK16:39, 17 July 2008 (UTC)[reply]
They might do this as a loss-leader, i.e. a way of getting notice taken of their journal. Many have a policy of making all articles free-access after six months, a year or two years. By that time the number of paid-for hits has probably decreased to nearly nothing anyway. They'll discuss the policy with the journal editor or editorial board. Different journals are aimed at different markets. Itsmejudith (talk) 18:26, 17 July 2008 (UTC)[reply]
Sometimes, when you publish in an academic journal, you can choose whether to make an article freely available or only available to pay for that journal's subscribers. To make it freely available, the author/institution typically has to pay thousands of dollars. Thus, it is not particularly common. Gjmulhol (talk) 19:58, 17 July 2008 (UTC)[reply]
What is the fucntional role of the foam head on a glass of beer? I've heard different explanations and found the beer and beer head articles lacking: the latter explained the physics behind why beer has a head, but not the gastronomy. Why is it important for some beers to have a certain kind of head/pour and not others? Variations I've heard usually mention some or all of the following: head...
...prevents the aroma from escaping prematurely
...retains carbonation
...guards against "oxidation" (though no one has ever told me of what component of the beer)
...keeps the alcohol from evaporating (unlikely)
...helps keep the beer cold (really unlikely)
I imagine some or all of these are probably true, but I can't find a decent source to back it up. In any event, the article could use a little expansion from a knowledgeable party. --Shaggorama (talk) 17:11, 17 July 2008 (UTC)[reply]
Most of these explanations range from unlikely to slightly silly. Beer head doesn't really affect carbonation or aroma, but is diagnostic of it (I'll explain below), and has little to do with decreasing beer oxidation (which is not a factor over the amount of time it takes to drink a beer). The simplest reason for the head on a beer is because people like it: it's aesthetically pleasing and adds a lovely texture to the entire beer-drinking experience. The size and color of a beer head is influenced by a number of factors, including the amount of protein in the beer (more protein equals more foam, and too much deviation from the standard for the style can indicate problems in the brewing process), the degree of carbonation (again, deviation from the standard can suggest bad things), and the temperature of the beer at the time of the pour (temperature greatly influences taste and aroma; also colder beers develop less of a head, while warmer ones may easily overtop). The perfect head on a beer is therefore a good indicator that all of these vital attributes are in a good balance. Hope this helps. – ClockworkSoul17:57, 17 July 2008 (UTC)[reply]
people like it or not. True, on mainland Europe, for example, most beers will be served with a nice head as it indicates that the beer is sparkling and fresh (hence the reason why some longlasting industrial beers have to add chemicals to produce the head) as opposed to flat or stale. But beware of your average UK pub dweller who is susceptible to throwing his pint at the barman if there is any head at all. I think the general feeling, somehow, is that it robs you of beer. From my experience though even in the UK some head is appreciated on a lager as long as its not more than a 1/4 inch thick or so. Also, each beer has its own optimal head (wether it's aesthetical or else I don't know) and you'll find some beers like the Belgian Duvel for which the head is higher than the liquid beer (although the glass it should be served in is thinner at the top so the foam might be less by volume). I think traditionally beers didn't really keeps for much more than a week and were at their best a few days after brewing, so the head is a good indication of how fresh the beer is. 190.190.224.115 (talk) 21:26, 17 July 2008 (UTC)[reply]
"I think the general feeling, somehow, is that it robs you of beer." Yes. If you've got a pint glass and two inches of head on the beer, you do not have a pint of beer. It's a way for the unscrupulous to short-change people. But some adverts are trying to convince the British to think in a European fashion about it and go for a beer with a tall head. Oh the lobsters! 79.66.90.252 (talk) 22:27, 17 July 2008 (UTC)[reply]
The foam on beer has been compared with the volt-amps-reactive (VARS) which come with electrical power (WATTS). Wouldn't be the same without'em. Edison (talk) 04:45, 18 July 2008 (UTC)[reply]
What is the coal-fired power plant with the highest capacity?
I was interested in finding out which coal-fired power plant has the highest capacity, and it seems to come down to two: Bełchatów Power Station and Kendal Power Station. According to the Kendal Power Station page, it is the "largest", which I assume to mean it has the highest capacity. But it has a capacity which is listed as being lower than the Bełchatów station is listed at. I can't find a good source for the capacity of either one of these, and Kendal uses the company's Web site as its source, which is hardly an unbiased source.
I guess I would like to know if there is a good source for this information, and what is a good metric for comparing the size of coal-fired power stations. -- timc talk 17:20, 17 July 2008 (UTC)[reply]
As coal-fired power plants are generally designed to produce electricity, maximum electricity production is probably a good metric. And you can probably trust the company's website for that sort of data. PlasticupT/C18:45, 17 July 2008 (UTC)[reply]
I suggest that the answer lies in the definition of "plant" versus "unit" as to where the largest coal burner is to be found. Edison (talk) 04:41, 18 July 2008 (UTC)[reply]
I can't find a site for Bełchatów, so determining its capacity is difficult. Wikipedia says it is 4400 MW, and Google suggests that this is correct[5][6]. If so, that is higher than the capacity that is listed for Kendal (4116 MW), even though Eskom says that Kendal is the largest. Perhaps the issue is that Eskom is using the superlative "largest", which doesn't necessarily mean that it has the highest generating capacity. But if that is the case, what metric are they using? -- timc talk 15:06, 18 July 2008 (UTC)[reply]
I too found a few spots using Google that confirm Belchatow is rated at 4400 MW. Another metric could possibly be total output in MWh, so if Belchatow has more downtime or more units out of service, it could rank lower. Another possibility is that someone at Eskom just decided to put it on their website. I can't find any reliable source that actually shows a comparison, just news articles that could be repeating the company's own claim. I would say perhaps the articles should be changed to show that Kendal claims to be the largest, although Belchatow has a higher rated output. Franamax (talk) 21:54, 18 July 2008 (UTC)[reply]
Hi all. I'm looking for information about a device that has been circulated around the web as a "levitation" or "antigtrav" device. The General layout is a (usually triangular) light wood frame with some (copper?) wires and a bit of electronics. As far as I could tell, theses things actually do hover, by "somehow" using electromagnetic fields to accelerate air downward. What are those things called, and how exactly do they work (or was it a hoax after all?) I wasn't able to find any information on Wikipedia, it would be grat if this stuff could be mentioned at Antigrav#Conventional_effects_that_mimic_anti-gravity_effects and perhaps corss-linked at EHD_thruster#See_also (even if this is a hoax i'd hope to find information about it on wikipedia).
Sure... but one of the things often claimed to use antigravity. And since that was more or less the only thing i could remember about it, having it under "Conventional effects that mimic anti-gravity effects" seems helpfull and correct. -- Duesentrieb-formerly-Gearloose(?!)13:39, 19 July 2008 (UTC)[reply]
Webless spider
What kind of 1 inch spider would build a short tube type burrow without a trap door under a countertop appliance and then wait at the entrance and chase passing ants no bigger than the tips of its legs? Is there a known spider that would chase such ants and if so how would it eat them if it caught them? -- adaptron (talk) 20:54, 17 July 2008 (UTC)[reply]
I hit "edit" all ready to post a smart-ass answer like "With its jaws, fool" and then realized - I don't actually know how spiders consume their prey, and damned if I can find it anywhere on the wiki. Anyone know? --Random832 (contribs) 15:36, 18 July 2008 (UTC)[reply]
I was going to point out that it could be any funnel spider and most likely the brown recluse. As for chasing prey - that is not normal for any spider I've seen - and I've seen a lot of documentaries on weird spiders. The most common spider will catch prey in a web. Then, there are the ones that wait in a hole (or similar) and surprise prey as it passes by the opening. Finally, there are spiders that drop down on prey from above. Chasing isn't really anything I've seen. As for eating them - spiders inject digestive fluids into the prey and then drink the digested insides back out. -- kainaw™15:52, 18 July 2008 (UTC)[reply]
Brown recluses catch prey by chasing and pouncing on them, rather than by catching them in a web. They are very speedy litle sprinters, and as a result are hard to kill. Edison (talk) 19:19, 18 July 2008 (UTC)[reply]
Firstly you must think of the research ethics. Are you sure it is ethical to treat one of each pair and not the other? Technically, you can randomise by generating random numbers in a computer package such as SPSS or even Microsoft Excel. But should you be doing this kind of research on your own without access to the advice of more experienced researchers? Itsmejudith (talk) 22:00, 17 July 2008 (UTC)[reply]
He said it's a study comparing two treatments, not a study comparing treatment to non-treatment. That's the standard way of doing such studies. I agree, however, that such studies should have the support of a qualified statistician from the start if they are meant to taken seriously - as Ronald Fisher apparently said, "To call the statistician after the experiment is done may be no more than asking him to perform a postmortem examination: He may be able to tell you what the experiment died of." --Tango (talk) 00:21, 18 July 2008 (UTC)[reply]
Yes, I should have read the post more carefully. Even so, ethics is also something that needs to be fully considered at the design stage. Itsmejudith (talk) 07:20, 18 July 2008 (UTC)[reply]
July 18
Over-the-counter diet pills/supplements
Do any of these things actually work? Just browsing my usual online pharmacy site whilst making my monthly nicotine gum order and I stumbled across several claims about 'fat burning', 'fat binding' and 'speeding up metabolism' by various products (some 'herbal', some 'scientific') that sound somewhat improbable... --Kurt Shaped Box (talk) 00:04, 18 July 2008 (UTC)[reply]
In general, they're of variable safety but minimally effective. Many contain stimulants of some sort (caffeine, ephedra, etc.); stimulants have a long history of use in weight loss products (and plenty of side effects that have limited their legal availability--ephedra & fen phen, for example). "Herbal" stuff is almost assuredly worthless: at best it's an unknown dose of caffeine, at worst the unregulated product is laced with more powerful stimulants and compounds that can cause serious drug interaction issues/side effects. — Scientizzle00:22, 18 July 2008 (UTC)[reply]
(edit conflict) We can't give medical advice. You should probably talk to your doctor if you are looking for a way to lose weight. Personally, I would be doubtful of such claims - the only kind of diet pill I can see working is an appetite suppressant. --Tango (talk) 00:24, 18 July 2008 (UTC)[reply]
No, I'm not looking to lose weight. I saw this stuff on the web and wondered how they manage to get away with making the sort of claims they are making about their products. It's quite common in UK pharmacies (real, brick and mortar ones too) to see products that I would personally file away in the quackery/placebo effect bin alongside the healing magnets and activated water. --Kurt Shaped Box (talk) 00:37, 18 July 2008 (UTC)[reply]
I think questions of efficacy can be handled without delving into handing out medical advice, but (of course) a physician would be an appropriate source of information regarding these products. Stimulants, by the way, are often appetite suppressants, having the duel effect of upping energy consumption while decreasing intake (and many unwanted effects, as well). I'd also note that, in the US, there is currently only one FDA approved, over-the-counter weight loss product: Orlistat. — Scientizzle00:41, 18 July 2008 (UTC)[reply]
Interesting, thanks. Some of the pills sold on the site were described as being able to bind to fats in the GI tract, creating large, inabsorbable (is that a word?) molecules which will merely 'pass through'. Does that sound like 'bunk' to you? --Kurt Shaped Box (talk) 00:47, 18 July 2008 (UTC)[reply]
Orlistat does work to prevent fat absorption, so it's possible that in the UK there are similar things on the market that actually do that. However, its method of action is to inhibit an enzyme that makes fats readily abosorbable, not work as some sort of fat aggregator--that sounds psudoscience-esque (but without more information, I can't be sure). — Scientizzle00:54, 18 July 2008 (UTC)[reply]
That page talks about them being on sale in the UK (in the last line), so I guess so... There's one born every minute. --Tango (talk) 01:06, 18 July 2008 (UTC)[reply]
(edit conflict) I've never seen them personally. I noticed the other day that my local pharmacy sells magnetic wristbands for arthritis relief though (FFS!). I've seen ear candles for sale in more than one place too. I'm currently reading through http://www.dietfraud.com/ - a lot of the stuff I've seen advertised does indeed sound like classic 'bunk', according to their writings... --Kurt Shaped Box (talk) 01:07, 18 July 2008 (UTC)[reply]
Heh, I was actually browsing through that site after I finished posting here last night/early this morning. It's amazing what some people will believe, isn't it? --Kurt Shaped Box (talk) 12:58, 18 July 2008 (UTC)[reply]
As someone pointed out somewhere (I forget exactly where), a lot of these things talk about 'unleashing the bodies natural healing abilities'. Magnetic wristbands often do, among others. Anyway, the point is... how would you describe the placebo effect? 79.66.90.252 (talk) 23:08, 18 July 2008 (UTC)[reply]
I'd say many of those might work in the short term, say by having you burn more energy as a result of taking a stimulant or causing you to eat less fat since now you crap your pants if you eat fat (because you're taking a fat binder that causes "anal leakage"). However, as soon as your body adapts and finds other calorie sources to make up for those lost, you likely will gain all the weight back and more. StuRat (talk) 21:25, 20 July 2008 (UTC)[reply]
Carbon dioxide benefit
What articles describe experiments using additional carbon dioxide to help grow more lush plants and what is the maximum percent concentration of CO2 that can be used? --adaptron (talk) 02:25, 18 July 2008 (UTC)[reply]
Also see Free-Air Concentration Enrichment, though those experiments are designed to test the general physiological and ecological effects of higher CO2 environments, not to look at deliberately using CO2 to increase agricultural productivity, which it sounds like you might be talking about. I'd also point you to Phytotron but it's just a single sentence right now. --Allen (talk) 16:31, 18 July 2008 (UTC)[reply]
first human lunar mission
why does this NASA pdf expect the first human lunar mission a decade from now?
Since the file in question shows the anticipated allocation of NASA's budget, "first human lunar mission" implies more than one future manned mission to the Moon is expected. --Bowlhover (talk) 08:13, 18 July 2008 (UTC)[reply]
I think it's pretty obvious that they mean "first" only in the context of their new push to return to exploration as a primary goal. APL (talk) 14:14, 18 July 2008 (UTC)[reply]
Carbon dioxide risk
The article on Carbon dioxide states that for indoor levels of CO2, "Concentrations higher than 1,000 ppm will cause discomfort in more than 20% of occupants, and the discomfort will increase with increasing CO2 concentration." ... "At 2,000 ppm the majority of occupants will feel a significant degree of discomfort, and many will develop nausea and headaches. The CO2 concentration between 300 and 2,500 ppm is used as an indicator of indoor air quality."
Can anyone confirm that since the article shows CO2 levels were 315 in 1960 and are 387 now there is a .004 exponential rate increase and that in 115 years levels will reach 600 ppm if this rate is maintained and there is no catastrophic change due to some unknown phenomenon? --adaptron (talk) 06:22, 18 July 2008 (UTC)[reply]
No, it's not currect to state that "since the article shows CO2 levels were 315 in 1960 and are 387 now there is a .004 exponential rate increase". In order to conclude from the measured data that the CO2 level was increasing exponentially and that it therefore would probably continue to increase exponentially, you would need many data points, not just two. Or to reach that conclusion on theoretical grounds, you would need a sound theory to support the hypothesis. --Anonymous, 21:20 UTC, July 18, 2008.
Our article on global warming shows projected levels between 541ppm and 971ppm by 2100, based on a large number of variables and potential actions. As the anon poster says above, you can draw any curve you want between 2 points, however your projection doesn't look all that far off. Franamax (talk) 21:30, 18 July 2008 (UTC)[reply]
It's always incorrect to assume unbounded exponential growth. I'm sure we've got an article on that logical fallacy somewhere. --Carnildo (talk) 21:32, 18 July 2008 (UTC)[reply]
If the blood supply is so important, why do institutions like the Red Cross base it on donations? Wouldn't it be smarter to pay people to donate? And if the shelf life is so limited, why don't they keep a DB of donors and ask them to donate in emergencies? Mr.K.(talk)10:10, 18 July 2008 (UTC)[reply]
I believe Freakonomics discusses this sort of thing. Once you add a monetary incentive, you remove the incentive of the "feel-good factor" of doing a good deed, and you add an incentive to cheat the system somehow. Plus, you have to spend money on paying donors and running the payments system. 81.174.226.229 (talk) 10:55, 18 July 2008 (UTC)[reply]
Our article blood donation explains that it is World Health Organization policy for all countries to move to a volunteer-only system. I believe the thinking is that paid donation creates an incentive for poorer people to give blood, and on average they are less healthy people, hence the greater potential for disease to be spread. My guess is that in most developed countries donors' contact details are kept on a database (unless they take a privacy opt-out). That's certainly the case in the UK. Itsmejudith (talk) 11:00, 18 July 2008 (UTC)[reply]
As for a database of donors, I receive a text message every so often from the Irish Blood Transfusion Board telling me that the blood stocks for my blood group are low, and to go and donate. It may be the same in your country (?). Fribbler (talk) 11:02, 18 July 2008 (UTC)[reply]
I don't donate personally but I've seen people receive cards before when there's a drive near where they live. My guess is O- donors may receive special requests when there's an emergency Nil Einne (talk) 07:44, 19 July 2008 (UTC)[reply]
Normally, in the US, the Red Cross or Lifeline Blood Services or whoever has free orange juice and cookies. Occasionally, they'll give away free t-shirts and other small prizes. I think the last time that the Red Cross came to my workplace to get blood donations, they offered free tickets to the local minor league baseball team's games. Dismas|(talk)14:37, 18 July 2008 (UTC)[reply]
From what I know in the US from my experiences is that they usually give SODA and cookies, even though you're not recommended to drink it after giving blood. And there are often organizations (radio, police, frats, schools) that organize blood drives, and that's usually when you see the tickets and t-shirts. --Wirbelwindヴィルヴェルヴィント (talk) 18:12, 18 July 2008 (UTC)[reply]
The drinks and snacks aren't to thank you for giving blood, they're to stop you fainting on the way home! It's important to replace the fluids, etc. you've just lost. You sometimes get vouchers for ice cream in the UK - particularly in student towns, I think. Ben and Jerry's is a common way of bribing students to do things! --Tango (talk) 21:20, 18 July 2008 (UTC)[reply]
I would guess most of these gifts to donors are in turn donated by whoeever they're coming from so it depends somewhat on who's willing to donate gifts for drive organisers to give to donors. Nil Einne (talk) 07:44, 19 July 2008 (UTC)[reply]
How is body mass index really defined?
The article can't seem to make up its mind. Let be a person's mass and let be their height. Is BMI defined as the dimensionless number
:The first example is identical to the second, only that the first have the units defined. These units do not cancel is the same as . Jdrewitt (talk) 10:21, 18 July 2008 (UTC)[reply]
The first example is dimensionless; he is explicitly dividing out the units. If my mass is 70 kg, the numerator of the first expression is (70 kg)/(1 kg) = 70, a dimensionless number. The denominator works similarly. The result of the division is thus also dimensionless. To answer the question, I've never seen a BMI with units attached, so I would guess that it is a dimensionless number, as produced by the first equation. But I have no source. -- Coneslayer (talk) 11:19, 18 July 2008 (UTC)[reply]
Body mass index is an index, not a measurement. That is why it doesn't have units. Unlike unit measurements where 1 meter is 1 meter regardless of who is measuring it, BMI is a statistical index based on the population. If anything, it could have been designed as a percentile. However, a simply index was chosen which is easily turned into a percentile. -- kainaw™12:08, 18 July 2008 (UTC)[reply]
BMI doesn't depend on the population, it's a number calculated from measurable properties of a person. What's considered healthy might depend on the population, but the number itself doesn't. The reason it isn't usually seen with units is simply because the units are always metres and kilograms, so there is no need to state them. --Tango (talk) 21:24, 18 July 2008 (UTC)[reply]
You are misreading what I probably miswrote. Perhaps the article states it clearer: "The body mass index (BMI), or Quetelet index, is a statistical measure of the weight of a person scaled according to height. As such, it is useful as a population measure only, and is not appropriate for diagnosing individuals." -- kainaw™03:31, 23 July 2008 (UTC)[reply]
BMI can be considered either as dimensionless or as having the unit kg/m^2. Take your pick between these two views:
(1) A person's BMI has the unit is kg/m^2 regardless of whether it's written. Dimensionless numbers result from comparing too identical types of quantities, such as two lengths or two velocities, so the units used in measurement do not affect the dimensionless number. For the body mass index, on the other hand, only kg and m can be used without introducing conversion factors.
(2) If we make the simple assumption that a person's BMI is (weight/height^2)/(1 kg/m^2), the BMI would be unitless, and the index is indeed almost always reported without any units. --Bowlhover (talk) 09:09, 19 July 2008 (UTC)[reply]
A Possible Method for Tachyon Formation and A Possible Method for Superluminal information transfer
Today while I was reading an article on tachyons, I suddenly thought about tachyon pairs appearing beside a black hole due to quantum fluctuations, and becomes "real" being sent by Hawking Radiation, which the article said "real" tachyons do not exist. Is this method of tachyon formation possible? please reply! And, I also thought that humans could create a machine that ejects multiple tachyons at different rates and places, and another receiver collects the tachyons, and "reads" their shapes and converts them into pictures or words that are understandable by humans. Perhaps, the sender may be able to send a line of tachyons coded with Morse code(special thanks to Morse!) like telegraph, and the receiver receives the data and decodes the pattern of tachyons into understandable symbols or words. Is this method of superluminal information transfer possible? Please reply!!! —Preceding unsigned comment added by Superwj5 (talk • contribs) 13:18, 18 July 2008 (UTC)[reply]
You realize that tachyons are hypothetical particles? That is to say, no one has ever seen one, and they may not exist, and if they do, we don't really know their properties. Could someone do this? Uh, maybe? But you're not going to get any kind of a real answer to that here, because you're essentially asking about science fiction. -- Captain Disdain (talk) 15:24, 18 July 2008 (UTC)[reply]
Also, your "questions" have more "I have a crazy theory" than "I have a question" to them. It makes it very clear that you are looking for discussion, not references. This is a reference desk. If you simply want to discuss your theories, there are thousands (if not millions) of discussion forums on the Internet just for that purpose. -- kainaw™15:31, 18 July 2008 (UTC)[reply]
I think you're being confused by two different uses of the word "real" in physics. Tachyons are not real in the same sense that Santa Claus is not real, whereas the particles in Hawking radiation are real in the sense that they're not virtual. -- BenRG (talk) 16:39, 21 July 2008 (UTC)[reply]
hypopthetical global warming
Hi. This is not homework, and is viewed from a theoretical standpoint. Consider 17°C (30°F) of global warming. What would happen to Earth's Flora and Fauna, its microorganisms, and humanity? What if this happened in 10,000 years? 4,000 years? 1,000 years? 600 years? 500 years? 300 years? Would we survive? Could negative feedbacks eventually bring on a cooling trend? What would happen with 5,000 ppm CO2? What about 60 metres of sea level rise? Thanks. ~AH1(TCU)17:26, 18 July 2008 (UTC)[reply]
That sort of temperature rise would lead to a major mass extinction event. There was a minor one associated with a 6°C rise 65 million years ago, which is the sort of rise expected soon with global warming (and all the older official estimates have turned out to be underestimates). Perhaps humans would survive, I'm not sure. It would make a good disaster movie. Dmcq (talk) 21:01, 18 July 2008 (UTC)[reply]
It's worth considering that before you consider "Could negative feedbacks eventually bring on a cooling trend" you likely have to consider how you got 17°C rise in the first place (if a negative feedback does kick in, why didn't it kick in earlier? Or did it already kick in but we somehow managed to release such an extreme amount of CO2 that we still managed to achieve such a rise?). I'm not sure but I think our current knowledge re: such an extreme rise is limited since must studies are concentrated on what is expected with what we're doing now or may be doing in the future rather then what conditions may lead to such an extreme rise (according to the latest IPCC "IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C". Of course we know that if we do have such a rise, it would be catastrophic Nil Einne (talk) 07:34, 19 July 2008 (UTC)[reply]
One of the possible causes of the Permian-Triassic extinction event, the largest extinction in Earth's history, is a temperature increase of 10 to 30 degrees Celsius (see http://news.bbc.co.uk/2/hi/science/nature/4184110.stm). Although the cause of the extinction is still not known with certainty, the scientists who proposed the above-mentioned warming as a hypothesis presumably had evidence that a 10-degree rise in temperature can cause 80% of species to perish.
5000 ppm is 18 times the pre-industrial CO2 level. Earth's temperature rises approximately 3 degrees for every doubling of CO2 concentration, so 5000 ppm implies a warming of 12 degrees. Of course, positive and negative feedback systems would have a great impact in such an extreme climate.
As for sea level rise, http://merkel.zoneo.net/Topo/Applet/ is a crude interactive tool that displays geographical maps for any user-entered sea level increase.
Hi. Yes, IPCC predicts 1.4 - 5.8C of warming within 100 years, and 6C would still be catastropic as Six Degrees: Our Future on a Hotter Planet says 6C is all it took for the P-T extinction to occur, and please say if you're using C or F, and Fred Pearce's book With Speed and Violence: Why Scientists fear tipping points in Climate Change details that the Hadley Centre predicts upwards of 10C (21F) within 100 years. Thanks. ~AH1(TCU)18:32, 19 July 2008 (UTC)[reply]
Sorry about the 6C I'd been thinking of his lowest timescale of 300 years which considering there's lots of coal tars etc will be hard to avoid. I should really have stuck to the IPCC limit of 2100. However the IPCC does has 6C within its error range which is quite worrying. Dmcq (talk) 19:34, 19 July 2008 (UTC)[reply]
I would think the total amount of habitable land would be about the same. Portions of the tropics and coastal areas would become uninhabitable due to high temperatures or flooding, but, at the same time, vast areas of Canada, Greenland, Russia, Sweden, Norway, Finland, and even Antarctica, would become habitable. The greatest threat to humanity might be indirect, as competition for those new resources could lead to global war. StuRat (talk) 21:12, 20 July 2008 (UTC)[reply]
I think that most places inhabited now would become uninhabitable or unpleasant. The loss of species would probably cause ecological collapse and therefore mass starvation. 98.198.9.137 (talk) 14:47, 23 July 2008 (UTC)[reply]
It may be true that the total inhabitable area will not change much, but the current economy is adjusted to the current climate. If fertile farmland becomes unusable for farming, agricultural output would decrease, the associated industries would suffer, and a recession would occur until the economy adapts. An economy established in Greenland or northern Canada would not produce in great quantities until far into the future. --Bowlhover (talk) 08:22, 24 July 2008 (UTC)[reply]
Peruvian tropical cyclones and the Humboldt current?
Hi. Why don't tropical cyclones ever occur in the southeastern Pacific? Yes, I know it's because the Humboldt current keeps the water there cold, even more so than in the South Atlantic, but what about during an El Niño? Wouldn't the water be almost as warm as the southwest Pacific? Or, is there too much wind shear? In a globally-warmed world, with stronger El Niños, would tropical cyclones develop there as in the South Atlantic? Or, does something else keep cyclones from forming there? Is it a high pressure system? If it is, then why when hurricanes in the Atlantic form occasionally where the Bermuda high should be, none form near the South American coast? Do Antarctic cold currents and winds keep the South Hemisphere too cold? Also, is the Humboldt current the main reason why the Galapagos islands are so diverse? Thanks. ~AH1(TCU)17:35, 18 July 2008 (UTC)[reply]
I could't find direct sources, but El Nino is defined by a surface temperature deviation of at least 0.5°C. The Humboldt current is about 7-8°C colder than one would expect water at this latitude to be. So even with El Nino going strong, the water is still quite cold. --Stephan Schulz (talk) 22:43, 20 July 2008 (UTC)[reply]
See this map. Even during the strong 1998 El Nino, the ocean temperature in the southeastern Pacific was only above the lower limit for hurricane formation, 28 degrees, north of 10 degrees south. Note that the ocean in the area was colder during a strong El Nino than the southwest Pacific was during a strong La Nina.
The second unfavorable condition preventing the formation of cyclones is indeed wind shear. See this paper, which addresses the issue of why tropical cyclones don't form in the southeastern Pacific.
This question probably just indicates my lack of understanding on CP-violation and 3-manifolds, but here it goes:
Let's say there was a group of flat-landers living on a Mobius strip, or if you like, a klein bottle. Now let's say one of the said flat-landers embarks on a journey around his universe. When the he returns, the other flat-landers find that his left and right sides have been switched, i.e. assuming flat-landers are anatomically similar to us, his heart is now on his right side. Of course to his point of view, his heart is on his left side, and left and right everywhere else is switched.
Now let's take this to a three dimensional universe on some kind of a generalized klein bottle. Another journeyman goes across the universe, this time with a bottle of kaons (Ignore in difficulties caused by their decaying and the likes.) When he comes back the kaons will violate CP-symmetry the other way now (and his heart would be switched too, I think). Would this be like having one side of a Mobius strip red and the other side blue, meaning there has to be a boundary somewhere, or could it prove that the universe is orientable? If I've got any of these facts or assumptions wrong, please let me know because I am trying to learn and I do not understand this stuff very well yet.
Forgive me if this is off-topic of your questions. I stopped reading after your assumption of the flat-lander's anatomy being switched. If you travel around a Mobius strip, you will not know you are doing so. You set off on a straight line. When you reach the point on the strip where you started - from the point of view of a 3-dimensional being - you are on the opposite side of the strip. Nobody was sitting around at your starting point will know you are there. You continue on another lap and return to the starting point and meet your friends. So, if the true circumference of the strip is 100m, you will claim it is 200m because you had no means of knowing you passed your starting point on the opposite side of the strip. -- kainaw™18:43, 18 July 2008 (UTC)[reply]
No, sorry Kainaw, you're taking the "paper strip" image too literally. A mathematical Möbius strip does not have any thickness; when you get around to where you started you do see your friends, but you are now oriented differently with respect to them. --Trovatore (talk) 18:50, 18 July 2008 (UTC)[reply]
Wow, Wikipedia really does have an article about everything. Although the article doesn't mention CP-symmetry, I'm guessing that no global distinction can be made for it as well. Now I have a new question: does anyone know if there are good reasons that the universe may be orientable or not. I realize it probably makes the physics cleaner if it is orientable, but maybe there is some evidence to the contrary perhaps? Anyways, thanks for the article Algebraist. Jkasd19:54, 18 July 2008 (UTC)[reply]
Zipcodezoo
Hello, Refdeskers! I hope this is the appropriate place to begin this discussion. I was wondering if any of you have an opinion on ZipcodeZoo. It's beginning to come to the top of the list on google searches for species and genera and thus is also beginning to show up on Wikipedia. There are about 190 pages on Wikipedia that mention or link to zipcodezoo [7]. Personally, I've found this resource to be unreliable to some extent. I believe it gathers data from various sources and presents it without a human eye looking over it, leading to situations where synonyms for species are wildly incorrect. Taxonomy is just as bad. See specific concerns at an archived discussion with WP:PLANTS: Wikipedia talk:WikiProject Plants/Archive18#ZipcodeZoo. I'd appreciate your thoughts on this. Is removal on sight acceptable? Hopefully with time it will become more reliable, but over the past year it hasn't changed much. --Rkitko(talk)23:50, 18 July 2008 (UTC)[reply]
Having reliable sources is one of the core policies of Wikipedia. I'd say ZipcodeZoo is neither authoritative nor reliable. Therefore, it shouldn't be used in citations, although the citations that ZipcodeZoo references may be good to use. It looks like the makings of a good resource, though, so I can see it in a list of external links. ~Amatulić (talk) 21:44, 21 July 2008 (UTC)[reply]
Thanks for your reply. Is there a better to post this question? WP:PUMP? I think it's a relatively small phenomenon so far, but I'd feel better with more input. Cheers, Rkitko(talk)22:40, 21 July 2008 (UTC)[reply]
Disadvantages of coilguns and railguns
What are the disadvantages of modern coilguns and railguns that need to be overcomed for possible infantry use? --Whuzatt23:52, 18 July 2008 (UTC)[reply]
The railgun page on wikipedia should give some insight. For larger applications, incredible amounts of energy is needed. launching projectiles also damages the tracks. Coolotter88 (talk) 02:17, 19 July 2008 (UTC)[reply]
The amount of energy needed is currently a technological hurdle. There needs to be improvements in portable energy before e-mag cannons see widespread use. Railguns can deliver more force, but the friction cause by the projectile sliding against the rails causes a lot of damage. Maybe if there were a way to coat the rails or the projectile in conductive plasma, that might solve the problem. ScienceApe (talk) 17:12, 19 July 2008 (UTC)[reply]
Then there is the magnetic field generated, which could permanently damage nearby equipment or make it temporarily inoperable. The magnetic pulse might also be detectable by the enemy (for them to use in target-acquisition or as a warning to take cover). StuRat (talk) 20:54, 20 July 2008 (UTC)[reply]
July 19
Obesity
Apart from being less likely to starve to death during the next famine, are there any health benefits of being overweight? --Carnildo (talk) 04:15, 19 July 2008 (UTC)[reply]
I don't know about obese people (especially extreme obesity), but slightly overweight people tend to have slightly better survival outcomes with various forms of cancer and modern treatments IIRC. On the other hand, being overweight (and especially sedentary) tends to increase the risk of getting cancer so... (And admitedly some studies seem to show the opposite e.g. [8] which suggests a lower survival rate in Chinese women) Nil Einne (talk) 07:24, 19 July 2008 (UTC)[reply]
I don't know of any real good effects of being obese. The article lists all these as negative factors though:
A recent (and controversial) study in JAMA suggests your final statement may not be accurate, CycloneNimrod. They conclude that "The net result [of their study] was that overweight was associated with significantly decreased all-cause mortality overall." Specifically, being overweight gives an apparent protective effect against causes of death such as tuberculosis, emphysema, pneumonia, Alzheimer's disease and injuries, but an increased risk of cardiovascular disease, some cancers, diabetes and kidney disease. When you balance the two out, the chubbies appear to be in the black. To be fair, the study didn't control for smoking and preexisting illnesses, so it could be skewed, but it does give one, ahem, food for thought. Rockpocket20:02, 19 July 2008 (UTC)[reply]
Obesity is bad, but there are potential benefits to being slightly overweight. Nil Einne gives one above, and I believe there are others, but I'm not sure what they are. --Tango (talk) 17:51, 19 July 2008 (UTC)[reply]
While obesity per se presumably has little biological selective advantage, remember that the ability to store large amounts of fat when food is plentiful is of great selective advantage--at least before modern times when food is abundantly available all year for many people. Then this physiological ability becomes non-adaptive. Seen in this light it is easier to see why becoming fat is so common, and why losing weight is so very difficult. Evolution has equipped us with the strong desire to eat greedily far beyond our immediate needs, because in the past it increased survival, and for women, the likelihood of having and nursing strong children.--Eriastrum (talk) 23:04, 19 July 2008 (UTC)[reply]
We've already touched on obesity preventing people from starving to death, but note that such starvation isn't always due to a lack of food. Many diseases cause a drastic loss of weight, which can be fatal, especially if not treated (say with a glucose IV).
Hypothermia has been mentioned, but I disagree with the statement that obesity is no help when wearing clothing. Obesity may be especially helpful when waiting in cold water for a rescue, for example, whether wearing clothing or not.
Obesity may also decrease the rate of drowning, because fat floats, and people with more fat float better. They esentially come with their own floatation device.
Then there is the absurd effect that some studies might indicate a reduction in the death rate from many other causes which seem unrelated to obesity, like homocide. The reason is that obese people are likely to die earlier, thus having less opportunity to be murdered. StuRat (talk) 20:49, 20 July 2008 (UTC)[reply]
AIDS Cure Deadline?
Despite the obviously long term nature of the search for an AIDS cure/vaccine, has anyone been quoted regarding any theoretical deadline by which we can expect it by? Or are things still in the "It'll be here when it gets here" stage? —Preceding unsigned comment added by Kenjibeast (talk • contribs) 04:40, 19 July 2008 (UTC)[reply]
I suspect that one day, potentially within my lifetime, there may be a cure (whether in the form of a vaccine or not). For now, though, I don't think anyone has much idea of when or how it'll be achieved. As Carnildo posted, that article may give a few hints. —CycloneNimrodTalk?10:09, 19 July 2008 (UTC)[reply]
Carnildo, is there reason to believe that it's impossible? Or perhaps I'm really asking if there is any consensus among scientists in the field that it might be impossible. Either way! I'm asking because from what I understand, there are promising discoveries being made, even if an actual cure still hasn't been found. It seems to me that at least some progress is being made, but is that just an illusion in terms of whether knowledge about HIV and fighting it has appreciably increased within the last, say, five years? -- Captain Disdain (talk) 10:27, 19 July 2008 (UTC)[reply]
It's definitely not impossible. For example, we could create a nanomachine, that could destroy the virus. Nanomedicine if you will. It's beyond our current level of technology, but it's possible. Incidentally, such a nanomachine would be capable of curing other RNA viruses like the common cold. ScienceApe (talk) 17:15, 19 July 2008 (UTC)[reply]
As noted in the article, HIV mutates very quickly, and the surface proteins that the immune system (or ScienceApe's magical nanotech) would use to recognize it change frequently and at random. --Carnildo (talk) 23:37, 21 July 2008 (UTC)[reply]
Well I would assume the nanomedicine would have a better method of identifying the virus than our own immune system. I wouldn't have any idea of how to do it, but I guess it would have to be some kind of logic program, which would ignore minor variations in the same kind of virus. ScienceApe (talk) 21:31, 23 July 2008 (UTC)[reply]
You rarely have anything more than guesses about the timescale for new inventions. The process basically involves trying lots of different things until you eventually find one that works (the skill comes in narrowing down which things to try). Since you don't know which one is going to work, you can't say how long it's going to take to find it. It's difficult to even give an expected time without knowing how many possible things there are to try (which is pretty much infinite) and how many of them are going to work (which could be anything from none to infinite). --Tango (talk) 17:49, 19 July 2008 (UTC)[reply]
Alcohol dimer formation
It is a known fact that organic acids form dimers by hydrogen bond attachment of the carbonyl group oxygen in one acid molecule (say molecule A) with hydroxy group hydrogen in another acid molecule (say molecule B) and the carbonyl group oxygen in B attaches with hydroxy group hydrogen in A as seen here:[9]. In organic alcohols, though, the hydrogen in a molecule(say C) attaches with the oxygen in another molcule (say D). Is the remaining oxygen of molecule C capable of attachment with the hydrogen of D (to form a quasi-acidic two way dimer), or, will the oxygen of C and hydrogen of D always attach with the hydrogen and oxygen of some other molecule? Leif edling (talk) 06:37, 19 July 2008 (UTC)[reply]
A dimer is possible, as is a trimer (3 in a ring).
A hydrogen from C will undoubtedly be hydrogen-bound to the oxygen in D, but I think it would be more likely for the oxygen of D to be bound to a hydrogen from another molecule, E, rather than C, in the liquid state. This way, a network of hydrogen bonds can be formed similar to that which water forms, but with less intensity. I've never heard of a single OH group simultaneously being an acceptor and donator to only one other OH group. --Russoc4 (talk) 14:49, 19 July 2008 (UTC)[reply]
Yes a dimer is possible, but mostly unlikely - reason - four membered rings are much less stable than 6 membered ring - note in carboxylic acid dimers the 'ring' structure' is hexagonal (though there are 8 atoms involved)87.102.86.73 (talk) 16:13, 19 July 2008 (UTC)[reply]
It shows that for n-hexdecanol in the solid the molecules form with OH groups in a line eg:
H
/
CCCCCCCCCCCCCCCCO
CCCCCCCCCCCCCCCCO
H \
\ H
OCCCCCCCCCCCCCCCC
OCCCCCCCCCCCCCCCC
H /
/ H
CCCCCCCCCCCCCCCCO HOxxxxxxxxxxxxxx
CCCCCCCCCCCCCCCCO
H \
\ H
OCCCCCCCCCCCCCCCC
OCCCCCCCCCCCCCCCC
H /
/ H
CCCCCCCCCCCCCCCCO etc etc
C represents CH2 etc, my rough interpretation.. as you can guess where the H bonds will be you can see the zig-zag formation.. This is only one layer - you might guess that the next layer will be reversed - so that the alcohol on top takes the position indicated by HOxxxxxxxxxxxxx ...87.102.86.73 (talk) 15:35, 19 July 2008 (UTC)[reply]
I'll guess and say that I'm certain that the type of arrangement above is that which occurs and not a dimer. Though a dimer may still form temporarily in the liquid.87.102.86.73 (talk) 16:15, 19 July 2008 (UTC)[reply]
Aspartame lead to drowsiness?
Why is it that when I drink diet drinks with aspartame it makes me drowsy, like when you've been awake for too long and your consciousness begins to lapse? Is it a known side effect? What causes this? --antilivedT | C | G08:27, 19 July 2008 (UTC)[reply]
Yea I've looked at that, doesn't really mention my effect. This is not exactly medical advice since I've already stopped drinking them; I'm just curious on why it affects me in this way while other people are seemingly fine taking it. --antilivedT | C | G10:32, 19 July 2008 (UTC)[reply]
One extremely far-fetched reason could be that the aspartame is breaking down into methanol in amounts significant enough to cause drowsiness. It's far-fetched because the amount of aspartame in your drink is probably minuscule, and certainly not enough methanol would be created to have any noticeable CNS depression. --Mark PEA (talk) 12:44, 19 July 2008 (UTC)[reply]
Do you commonly drink diet caffeinated drinks, but are now drinking caffeine free drinks? It could be a psychological effect if your body/mind has paired drinking caffeinated drinks with the flavor of aspartame, but has now suddenly been subjected to caffeine free drinks of the same or similar flavor. --Russoc4 (talk) 14:54, 19 July 2008 (UTC)[reply]
Or, similarly, you used to drink the non-diet versions and simply have a lower blood sugar level now - drowsiness and loss of concentration are symptoms of hypoglycaemia. --Tango (talk) 17:43, 19 July 2008 (UTC)[reply]
Hmm not really, I don't usually drink caffeinated drinks at all. And even so diet Coke has caffeine is well so if anything it should give me a "boost" as well. I still get this if I drink both diet and non-diet soft drinks at the same time or drinking it while having a meal, so I'm pretty convinced it's the aspartame or anything else that's different between diet and non-diet soft drinks. --antilivedT | C | G23:19, 19 July 2008 (UTC)[reply]
You could be allergic to aspartame, I suppose - you would need to talk to a doctor if you want to find out for sure. --Tango (talk) 00:17, 20 July 2008 (UTC)[reply]
No. (Which should be fairly obvious from the scheme itself—if the dominant trait was always "better", why would there be recessive traits at all?) --98.217.8.46 (talk) 19:07, 19 July 2008 (UTC)[reply]
It's not "pretty subjective" as to whether dominants are always better. The answer is "no". As to whether some dominants are better than some recessives, sure, and all other combinations. There are some dominants that will kill you right out, there are some recessives that will kill you right out. --98.217.8.46 (talk) 19:35, 19 July 2008 (UTC)[reply]
I can't think of a recessive allele that "will kill you right out", if you inherit it in a recessive manner (i.e heterozygous with a non-harmful dominant allele). Could you give an example? Rockpocket19:42, 19 July 2008 (UTC)[reply]
I was referring to two recessives. I would be very surprised if there weren't some heterozygote combinations that had non-harmful dominants that were fatal to the organism, though they would be rare for simple obvious evolutionary reasons. --98.217.8.46 (talk) 21:13, 19 July 2008 (UTC)[reply]
Assuming "kill you right out" means before you can reproduce (which is what is significant for evolution), then the only way you could get a allele that would kill you right out with only one present would be by mutation. Mutations often kill the organism pretty quickly - usually before birth, as a miscarriage. If it's having an effect, though, then surely it isn't recessive, by definition? Part of its function may be recessive, but the bit that's killing you clearly isn't. --Tango (talk) 21:31, 19 July 2008 (UTC)[reply]
That was my reasoning too, a dominant would have to be a de novo mutation in the germline and a recessive, by definition, wouldn't kill you right out. However, it is probably correct that the are scenarios where two recessive alleles (at different loci) could combinatorially "kill you right out" if inherited, one from each parent. I guess it would be a form of additive haploinsufficiency. I can't think of any example of that either, but I'm sure there are some. Rockpocket22:08, 19 July 2008 (UTC)[reply]
I hadn't thought of that. I've never heard of anything like that, but I can't see any reason for it not happening. --Tango (talk) 00:15, 20 July 2008 (UTC)[reply]
Dominance is relative. For example, a dominant allele for a receptor will be one that has a dominant function. A normally functioning receptor will have a dominant function in comparison with one that lost its regular function. In this case, the allele that encodes the normal receptor is the dominant allele and it may well be "better" (because we may need that receptor to function properly). However, another receptor allele may encode a receptor that is constitutively active (it keeps signaling an never stops). This allele will be dominant to the normally functioning receptor. However the regular allele may well still be "better" (because a always active receptor could be just as problematic as a never active receptor). In this case dominance does not equal better. But there are times when either lack-of-function and gain-of-function are better than the regular-function alleles, it all depends on what the environment is the genes are working in. Rockpocket19:42, 19 July 2008 (UTC)[reply]
Summarizing: the dominant trait tends to be the better one, for the simple reason that if weren't the better one it probably would have been selected out, whereas recessive alleles are subjected to less selection pressure. But the question asked if it's always better, and the answer to that is certainly no. --Trovatore (talk) 21:56, 19 July 2008 (UTC)[reply]
If I'm not mistaken, the current model of the universe is that it will continue to expand until even galaxies burn up and fly apart.
My only thought is of black holes. From what I understand, black holes do evaporate at a rather slow rate (see Black_Hole#Evaporation, but that currently the Cosmic background radiation is easily enough to offset this. However, in a situation in many tens of trillions of years, would the Cosmic background radiation have decreased in magnitude enough that it would allow very slow disintegration of the black hole? In this case, there would be essentially nothing left of the universe.
This, of course, excepts any circumstance which we cannot foresee (e.g., another big bang occurring very far away, unexpected reactions from dark energy). The Evil Spartan (talk) 19:50, 19 July 2008 (UTC)[reply]
I can't source it at present, but a cosmology talk I went to a few years ago featured a (very long) future epoch in which most of the mass of the universe was in very slowly evaporating black holes. There won't be nothing left after this, of course (the holes don't evaporate to nothing; that would violate energy conservation), but they'll be nothing very interesting. Algebraist19:54, 19 July 2008 (UTC)[reply]
See Heat death of the universe. Under your scenario (which is one of the likely ones), you would end up with nothing but radiation and individual sub-atomic particles (which ones isn't certain - protons may or may not decay over extremely long timescales) just floating around doing nothing much at all. This is called heat death. --Tango (talk) 21:25, 19 July 2008 (UTC)[reply]
Evil Spartan: your first sentence seems to be referring to the big rip. It is one of the posited fates of the universe, but the consensus seems to be that the ironically-named heat death is the most plausible. As for whether the CMB will eventually become cool enough for Hawking radiation to occur, the answer is yes, as the CMB has already cooled from 3000 degrees Kelvin to the current 2.7 degrees. A calculation using the equation :, found here, shows even a black hole of 100 solar masses requires the CMB to be lower than a few nanokelvins in temperature before its mass starts decreasing. --Bowlhover (talk) 09:11, 20 July 2008 (UTC)[reply]
I think many people are confused by the exponential growth of the scale factor in the Lambda-CDM model. Exponential expansion isn't nearly as catastrophic as it sounds. It won't rip the Milky Way apart no matter how much time passes. The fate of the galaxy in this scenario is plain old 19th-century heat death. In the big rip scenario (which is probably wrong) the expansion is faster than exponential—in fact the scale factor diverges to infinity in a finite time. -- BenRG (talk) 17:14, 21 July 2008 (UTC)[reply]
I did, but I am not seeing stuff I need: it has stuff related to colonizing the solar system (or a galaxy a general), but not what I am looking for which is "a manual for colonization of a random planet (or system) out there".--Piotr Konieczny aka Prokonsul Piotrus| talk 02:30, 20 July 2008 (UTC)[reply]
If by "random planet" you mean you want one manual suitable for any planet, then you won't find one, since different planets require different methods of colonisation. For specific planets, there's plenty of information out there, our articles linked to in the Space colonization article should get you started. --Tango (talk) 02:38, 20 July 2008 (UTC)[reply]
Cool. I've often pondered how I'd go about setting up a colony under the sea, in international waters. Nice to see others considering it and the implications :D 79.66.13.38 (talk) 19:59, 21 July 2008 (UTC)[reply]
Assuming we're thinking of the same thing, yes (as an aside, the common name is wrong and seriously misleading). I don't think the OP's question has an answer. Algebraist23:21, 19 July 2008 (UTC)[reply]
I agree that the question is misleading. What they are really asking is what the "____ rating" is at gasoline stations that tells you how likely it is that the car engine will "knock". However, as few modern cars have trouble with knocking any more, engine performane isn't likely to be an issue unless you buy poor quality gasoline at some nonane gas station. StuRat (talk) 20:29, 20 July 2008 (UTC)[reply]
Lately, I have heard discussion regarding the possible production of a new ice age due to the effects of global climate change.
Purely theoretically, how would an ice age effect Hay Fever sufferers? That is how would hay fever, being a seasonal disease, react to a drastic reduction in temperature. Specifics would be appreciated regarding the effect this new ice age would have on the various plants that cause hay fever. Would the cold affect pollen production, etc. —Preceding unsigned comment added by Kenjibeast (talk • contribs) 22:03, 19 July 2008 (UTC)[reply]
Different hay fever suffers are affected by the pollen of different plants. A significant change in temperature will change which plants grow where and at what times during the year. That will probably makes thing better for some suffers and worse for others (including some that weren't really sufferers before if new plants start growing where they live). It may well be better for everyone for a short time until the plants adjust, since there will simply be less plants growing successfully. --Tango (talk) 00:14, 20 July 2008 (UTC)[reply]
A shorter spring and colder summer would likely reduce the over-all pollen in the air. Then again, it might get worse depending on local ecology and how exactly your weather is being impacted. For example, some desert areas might get more rain encouraging more plant growth. ---J.S (T/C/WRE) 03:28, 20 July 2008 (UTC)[reply]
I would expect it to have a similar effect on the analagous structure in the female anatomy (you can decide whether to take clitorally all the things I say). StuRat (talk) 20:21, 20 July 2008 (UTC)[reply]
Is the universe's expansion speeding up or slowing down? I always thought it was slowing down but now someone has confidently asserted to me the opposite. I have looked at the wiki page on Expansion of the Universe but I don't think it says there (a lot of it was quite technical).
And yes, it is used to raise blood pressure in patients with dangerously low levels, either as an IV or given orally (say as a broth). Low blood pressure is a common result of dialysis, for example, and this is a common treatment. StuRat (talk) 20:10, 20 July 2008 (UTC)[reply]
One of the main components of olive oil comprises the majority of Lorenzo's oil, a substance which is used in conjunction with a controlled diet to treat adrenoleukodystrophy. The oil is still being evaluated by the FDA, but it's discovery was impressive and effective enough to merit the production of an academy award nominated film. --Shaggorama (talk) 06:09, 21 July 2008 (UTC)[reply]
Most drugs have side effects. It might be a good idea to look at the article for the specific drug you are interested in. Or consulting a doctor, if this relates to a specific medical concern.--Fangz (talk) 13:17, 20 July 2008 (UTC)[reply]
You may also want to read Statins. While not without side-effects you'll probably come across a lot of talk discussing statins as a sort of wonder drug given their general relatively high safety while having a relatively high success in lowering cholesterol. One concern, as is not uncommon in treating any condition diet related is that it's generally far better to modify/improve one's diet rather then to go on drugs, not just to avoid side effects of drugs, but also because of the other likely benefits of an improved diet Nil Einne (talk) 18:10, 20 July 2008 (UTC)[reply]
Yes, the lack of a good diet is a concern. I'd even go further and argue that some people may allow their diets to significantly worsen if they think some "miracle drug" will solve all their health problems for them. StuRat (talk) 20:02, 20 July 2008 (UTC)[reply]
asteroid - earth impact
How precisely can we detect in advance menacing asteroids that might crash on earth? How do the predictions improve as the object approaches? At what moment are we able to pinpoint an area where it will crash? Is there a range of speeds asteroids find themselves in, do different speeds change the force or probability of an impact? Could one bounce off the atmosphere if it arrived a low angle? I read Asteroid impact but couldn't find the answers. Thank you. 190.190.224.115 (talk) 14:10, 20 July 2008 (UTC)[reply]
Using radar, we can get extremely precise measurements, often a long time in advance. I think the asteroid needs to be quite close to get such measurements, but there are often close approaches to Earth before the one that could result in a collision, so we can take the measurements then and project the path forwards. Where it will hit depends on the exact time of the collision. Working out the thin path that the asteroid could hit is quite easy, since it just depends on the direction the asteroid is coming from, working out where on that path it will hit requires exact timing, and that requires much more accurate measurements. We would probably still get that some time in advance. I would expect asteroids can bounce off the atmosphere, although I'm not sure it's very likely - there's probably a very narrow range between where it becomes shallow enough to bounce and where it misses entirely. --Tango (talk) 17:28, 20 July 2008 (UTC)[reply]
The difficulty isn't just in taking precise measurements of location, direction, and velocity, but is complicated by the fact that asteroids can change direction. This change, while slight, can significantly affect whether one will hit the Earth several passes later. Changes in direction are often due to interaction with other objects, but not always in a predictable manner. For example, while passing a planet or the Sun, tidal forces or sunlight can melt ices, which can then be vented. Those can change both the mass and trajectory slightly. StuRat (talk) 19:58, 20 July 2008 (UTC)[reply]
Can someone help me in my own noble pursuit of all the world's (scientific) knowledge?
What would be the proper order to read your science articles so I can become a scientific personality with a steel trap mind? I mean someone says " .... my milkman, 1846, berylium, and the tenth law of thermodynamics?" I would immediately reply "My good man, your statement about the nonexistant 10th law of thermodynamics strikes I, a well known intellectual powerhouse in the esteemed scientific community, as peplexing and oddly prophetic. For it has been determined, by a barrage of outside the box labrotory research, that the math, using a newly, sometimes controversial property discovered by a still top secret learning facility, is indeed correct. Your milkman will discover 6 more laws of thermodynamics! ]:)
You can read them in any order. Science does not have a starting point. You study. If you find something that you do not understand, you study that. If that leads to something you do not understand, you study that. You continue until you understand the first thing you were reading. As for being respected... you will need a PhD. Make a list of the top 100 scientists of all time. You will have a handful that lived before the invention of the PhD (so they don't have one). You will have a couple that didn't get a PhD for one reason or another. Then, the majority will have a PhD. Why? If you are too stuck up or lazy to get a PhD, why should all those who got theirs want to spend their time listening to you? -- kainaw™19:34, 20 July 2008 (UTC)[reply]
PhD is certainly the qualifier. All those man-hours put into achieving a doctorate, shows that you are a dedicated scientist in your field, and worth listening to. No one would care about what Miss Teen South Carolina thinks of blackholes or general relativity, but lots of people listen when Carl Sagan or Michio Kaku talk about them, because they know what they are talking about. ScienceApe (talk) 20:38, 20 July 2008 (UTC)[reply]
I don't think that's true at all. A PhD is nearly a requirement if you want a career in academia, but respect in academia is almost entirely a function of what you publish. Anyone who does look at your educational history will be more interested in the schools—a BA from Berkeley is worth a lot more than a PhD from Columbia Pacific University. I think professional astronomers appreciate Sagan's popularization of astronomy, but I don't think they'd rate his scientific work as especially memorable. Kaku I think is little short of a crackpot. Jack Sarfatti is an outright crackpot, and he has a PhD in theoretical physics from UC Riverside. There's a popular perception that anyone who can get a PhD must know what they're talking about, but sadly it isn't true. Anyone can get a PhD if they try hard enough; most people are just smart enough not to bother. -- BenRG (talk) 12:37, 21 July 2008 (UTC)[reply]
If you want my, totally biased advice: a great way to get a very generalist understanding of science is not to study science itself, but to study the history of science. If you read through the article on History of physics and took the time to look into the sub-articles linked to there, you'd have a great, great understanding of physics for practical, conversational purposes. Could you set up an experiment yourself? No. That takes formal training for the most part. Could you carry on a conversation about the relevance of the expanding universe? Yes indeed. Could you probably find yourself with a lot to say on the topic of string theory, relativity, and the philosophical implications of quantum mechanics? Yes you could—and frankly, if you aren't actually going to be whipping out your calculator right there, I'm not sure trying to parse through all the equations is going to get you very far anyway. Just my two cents. --98.217.8.46 (talk) 00:29, 21 July 2008 (UTC)[reply]
Having a PhD is not a requirement for being smart, or a good scientist. To be a good scientist, it is all about the mindset and philosophy you are in. A PhD is merely a good sign of one. Freeman Dyson is a famous physicist and Planck Medal winner who hates PhDs. Just wanted to get that in there. Mac Davis (talk) 03:43, 21 July 2008 (UTC)[reply]
You're only going to read (with dedication) if you're interested, and you'll talk more about subjects you're interested in as well. I'd suggest focusing your study on areas that fascinate you and follow tangents as they arise. You might also want to start brushing up on lay-science magazines; it sounds like you're interested in physics, so I'd suggest something like Scientific American or Popular Mechanics. --Shaggorama (talk) 06:24, 21 July 2008 (UTC)[reply]
I for one don't like popular science magazines at all. They just leave you "OK, black holes are like vacuum cleaners of space, but how does it really work.". Reading Wikipedia, for example, is much better. —Bromskloss (talk) 15:02, 21 July 2008 (UTC)[reply]
Don't forget to regularly read the Wikipedia Science reference desk (like you are now), I learn lots of new things everyday in just a 5 minute visit to this place. --Mark PEA (talk) 15:12, 21 July 2008 (UTC)[reply]
How does the odor of rotten food make us gag?
I suppose the "why" is a survival mechanism, so that we won't ingest foods that have been taken over by possibly noxious or even toxic bacteria. (Please correct me if I'm wrong.) What I don't understand is how this works. I had to get within arm's length of some overage potatoes today, last week it was a (refrigerated) leftover portion of baked tilapia. My few experiences with natto also made me gag almost to the point of retching. The pharyngeal reflex page wasn't much help, though I've also had this difficulty when clenching my teeth around those cardboard-covered dental X-ray film holders. Advice on avoiding this reaction would be helpful, but I'll settle for understanding it better. -- Thanks, Deborahjay (talk) 19:30, 20 July 2008 (UTC)[reply]
Yes, evolution is certainly why. As for how, I don't think it's anything mysterious. Your nose detects various chemicals in the smell and sends the signals to the part of your brain that analyzes the info. It compares it to a list of chemical combinations it recognizes as "rotten food" and sends the appropriate response to your body. That list of chemical combinations recognized as rotten food is somewhat interesting, though. It's partly inherited, but also partly learned. If you've ever eaten a food that had gone bad and then made you violently ill, let's say eggs, that may very well cause all eggs, fresh or not, to be recognized, from then on, as "rotten food". StuRat (talk) 19:49, 20 July 2008 (UTC)[reply]
The "how" is a involuntary muscle spasm and an emotional reaction. As with many involuntary reactions you can learn to suppress it, if you for some reason have a need. Garbage men learn that trick fairly quickly, I'd bet. ---J.S (T/C/WRE) 00:09, 21 July 2008 (UTC)[reply]
Actually despite what StuRat might think, the mechanism behind the gag reflex in response to certain odors is mysterious. The reason is that it appears to be largely innate, and not learned. That means that there is some genetically hard-wired neural network that encodes the odor-to-behavioral response. This type of innate response to odors is not unusual in animals, but they typically detect such odors with their vomeronasal organ which projects neurons directly to regions of the brain that mediate innate responses. The problem is, humans do not have a vomeronasal organ. Which means we detect the odors through or main olfactory system or one of the mysterious olfactory sub-system such as the septal organ or the Grüneberg ganglion (these are so mysterious, in fact, we don't have an article on them). Yet the neurons in the these systems project to cortical regions and don't appear to mediate innate responses. So the answer is that no-one really knows how certain smells appear to be innately aversive in humans. Rockpocket01:42, 21 July 2008 (UTC)[reply]
This isn't sourced, but I don't think I agree that it's not learned. Have you seen game shows like Fear Factor where the contestants have to eat century egg? I enjoy an occasional one "fresh" (haha, fresh century egg) out of the shell, as do many Chinese, but the people on the shows always gag. So in some ways, it has to be at least partially learned. --Wirbelwindヴィルヴェルヴィント (talk) 14:54, 21 July 2008 (UTC)[reply]
Like anything in the nature vs nurture debate, the truth is likely to lie somewhere between. Also, like I said before, it's possible to "learn" to suppress some types of involuntary reactions. ---J.S (T/C/WRE) 18:05, 21 July 2008 (UTC)[reply]
Blowing up nuclear powered vehicles
Lets say a nuclear powered vehicle like an aircraft carrier or a nuclear sub is attacked and destroyed with conventional weapons. Would the vehicle explode in a nuclear explosion, or would the explosion be no different than a similar conventional vehicle blowing up? Would there be radioactive contamination? ScienceApe (talk) 20:33, 20 July 2008 (UTC)[reply]
It's very hard to start a nuclear explosion (fission or fusion), and virtually impossible to do so with reactor that is designed specifically to avoid that occurrence. You'd get somthing like a dirty bomb, just dispersing all that nuclear material as a contaminant not trigger any further nuclear reaction. DMacks (talk) 20:36, 20 July 2008 (UTC)[reply]
(ec) There would certainly not be a nuclear explosion -- the fuels in such a vehicle are not weapons-grade in the first place, and even if they were, making a nuclear explosion is difficult; it requires very fussy design. Not gonna happen by accident. Radioactive contamination is certainly plausible -- I don't know what if any steps have been taken to prevent that in a war scenario and would be interested in finding out from someone who know --Trovatore (talk) 20:37, 20 July 2008 (UTC)[reply]
Actually US nuclear subs run on 93% enriched uranium, I do believe (and this article seems to claim such as well). It's not uncommon for small propulsion reactors to run on HEU—you get a lot more energy out of a lot less material that way (most research reactors used to run on HEU until somebody figured out that was a very bad idea). But no, you wouldn't get a real nuclear explosion, even with that fact being true, though you could get secondary explosions—e.g. inadvertent generation of hydrogen gas, that mixes with oxygen, that ignites, and spreads a lot of nasty stuff all over the place. You could imagine the fuel melting and forming a critical mass or two on the bottom of the reactor, which would result in neutron fluxes and maybe very tiny explosions but that's about it. --98.217.8.46 (talk) 21:40, 20 July 2008 (UTC)[reply]
Yes. ICF contamination is just from the material holding the reactor together, mostly. An actual fission reactor is constantly producing highly radioactive substances in great quantity. ICF has very mild contamination risk compared to fission. --98.217.8.46 (talk) 21:40, 20 July 2008 (UTC)[reply]
I question the "great quantities" part. Certainly the quantity is less than or equal to the mass of nuclear fuel lost during the reaction, which is quite low. StuRat (talk) 03:39, 21 July 2008 (UTC)[reply]
Yes, but the reaction products typically have much shorter half-lives, and therefore are much more radioactive, than the fuel. So while the quantity might not be large as measured in kilograms, it's a lot as measured in curies (or, more modernly, Bequerelsoops, I guess it's becquerels, but who really knows what those are?). --Trovatore (talk) 03:51, 21 July 2008 (UTC)[reply]
And I was referring to it relative to the ICF as well. A fission reactor contains far greater quantities of far nastier poisons than something that is only getting somewhat irradiated by a bunch of neutrons would. I am not trying to be anti-fission here, just pointing out that the production of rather nasty waste is an inevitable side-effect. ICF will irradiate its containment structure with neutrons which should induce some radioactivity but it's not going to be anything as bad as actual fission products. --98.217.8.46 (talk) 17:08, 21 July 2008 (UTC)[reply]
Depending on the details of the attack, it's quite possible that the reactor would survive intact (probably not watertight, but recoverable intact). Large metal objects have survived remarkably close to nuclear explosions. If the explosion was some distance away from the vessel, and ideally with the large bulk of the vessel between it and the reactor, then you might well expect the reactor (which is very heavily constructed indeed) to be ejected intact and deposited on the sea floor as a (warped, leaky) whole. -- Finlay McWalter | Talk20:53, 20 July 2008 (UTC)[reply]
It might also depend on the specifics of the reactor. I recall a number of scares (though only over contamination rather than nuclear explosion) involving nuclear reactors on submarines during the cold war. (E.g. Soviet submarine K-19) What almost happened by accident can happen also by malice. See [10] for a list of such accidents.--Fangz (talk) 22:37, 21 July 2008 (UTC)[reply]
Seagull dawn chorus of squawks
Why do they make so much noise as soon as it starts getting light in the morning? I looked out of my window today after they woke me up and saw them just flying around squawking loudly at each other. —Preceding unsigned comment added by 90.242.57.76 (talk) 20:51, 20 July 2008 (UTC)[reply]
Our dawn chorus article says that songbirds start to sing at dawn, often for territorial reasons. Less melodious, but the seagulls are doing the same. If you're in the UK/Europe, the seagulls have young in their nests at the moment so the parents are defensive. Watch out, because they sometimes circle and threaten to dive-bomb you. Itsmejudith (talk) 22:34, 20 July 2008 (UTC)[reply]
There is a Herring Gull nest on my roof this year. When it gets to about 4am, the chick is all "cheep! cheep! cheep! cheep! cheep!" whilst the mother (or father) gabbles/clucks away softly. It goes on all day - unless the chick is napping. The early-morning squawking gulls may also be on the look out for anything edible that has found its way onto the street overnight. When a gull spies food, it generally loudly announces the fact - which starts off a chain reaction of squawking amongst any other nearby gulls. --Kurt Shaped Box (talk) 23:26, 20 July 2008 (UTC)[reply]
Why would they announce it, knowing that this causes all the other gulls to try to steal their food ? Not the brightest, are they ? StuRat (talk) 15:34, 21 July 2008 (UTC)[reply]
I don't know for certain - but I suspect that any gull discovered feeding at a significant find without first notifying the rest of the flock will be on the receiving end of some heavy 'social pressure'. OTOH, the gull that spots the food might merely be giving a (fruitless) warning to the rest of the flock to stay away from his find... --Kurt Shaped Box (talk) 16:30, 21 July 2008 (UTC)[reply]
That said, you want to take safety precautions like making sure not to short the battery. Theres about a thousand different things that could go wrong in this process. If you are not an expert, please make sure to consult with one before doing anything crazy. In particular, do NOT short the battery in order to get current through the wire. EagleFalconn (talk) 14:56, 21 July 2008 (UTC)[reply]
It's not that likely that someone will be selling one. Firstly for magnets other things often get used in preference including ferrite (iron oxide).
Buying 10 kg of iron is relatively simple though. Was there any particular shape. If you just want a magnet with iron and other things in that should be possible, though 10kg is a big magnet.87.102.86.73 (talk) 19:05, 21 July 2008 (UTC)[reply]
meh, a car battery isn't going to do much harm. Shorting circuits is generally a bad idea, but car batteries don't have enough juice to really do damage. PlasticupT/C19:11, 21 July 2008 (UTC)[reply]
That's dangerously wrong. The amount of energy in a car battery is up in the megajoules, which is plenty to start a fire or make a small object dangerously hot. See http: //www.popularmechanics.com/automotive/how_to/4213127.html for an example. --Anonymous, 22:06 UTC, July 21, 2008.
Check your phone book for local businesses that do custom metal work. You can get solid square bars of metal in any size you need. ---J.S (T/C/WRE) 21:32, 21 July 2008 (UTC)[reply]
An educational supply business may be able to sell such a magnet. Back in school I remember a U shaped magnet that was pretty strong. When you dropped an aluminum plate between the poles it would only fall about 1 mm per second due to eddy current damping. Graeme Bartlett (talk) 01:46, 22 July 2008 (UTC)[reply]
Consider hiring someone to magnetize a hunk of iron of the specified mass using an electromagnet. That is how magnets are created in recent centuries. Edison (talk) 04:30, 22 July 2008 (UTC)[reply]
To make a powerful electromagnet, you should use a U shape or a disc shape, so that both poles can be applied to the thing you wish to lift, or to the area where you want the powerful magnetic field. The density of Iron is 7.874 g·cm−3, so you need a volume of 1270 cm3. If you could find iron bars for sale, you could take three pieces to form the core into a U shape, and bolt them together, allowing three coils to be slipped over the core on the two legs and the top. Any length of core which is not being magnetized by a coil will decrease the pull of the magnet. What you are likely to find comercially available today is not Wrought iron such as Michael Faraday used to create the first strong electromagnets in the 1830's, but Carbon steel. You should review the magnetic properties of the various forms of iron, because they differ in the intensity of magnetization the accept and retain. soft iron, like a nail, quickly loses its magnetisation, while "hard" ferrous materials retain their magnetisation better. If you are building an electromagnet, you need a material which becomes demagnetised when the current is switched off. If you wish to magnetize the iron and create a permanent magnet then a "hard" ferrous material or modern rare earth magnetic materials would create a strong, long lasting magnet. If you just literally want a 10kg chunk of magnetized iron or steel, you might buy a big sledgehammer and magnetize it with a coil which can be slipped aroung the head of the sledge after the handle is removed. A sashweight is another big hunk of iron which could be easily magnetized, but a bar magnet will not be as strong as a pot or U magnet. You could also take an old transformer remove part of the core, and use the rest as an excellent electromagnet, but a weaker permanent magnet, due to the type of iron used. A machine shop might have scrap pieces of iron bar or rod they would sell at a bargain price. An ag=ngle or I beam would be undesirable since a coil would not fit well around it. Edison (talk) 16:50, 23 July 2008 (UTC)[reply]
Microwave oven
Can someone explain briefly (without too much technical or scientific lingo) why you can't place metal / aluminum foil / etc. in a microwave oven ... and what exactly would happen if you do? Also ... why is it that food tastes "different" when cooked in a microwave oven versus a conventional oven? Thanks. (Joseph A. Spadaro (talk) 02:48, 21 July 2008 (UTC))[reply]
See Microwave_oven#Dangers for the answer to your first question. The short-short version is that a piece of metal will act like an antenna, converting the microwaves into electricity. Depending on the shape, size, etc of the metal, that can cause various problems. Metal twist-ties often catch on fire, for example. APL (talk) 03:19, 21 July 2008 (UTC)[reply]
That's interesting. Hmmmmmm. Do we have any technology that takes advantage of this phenomena of metal turning microwaves into electricity? ScienceApe (talk) 03:37, 21 July 2008 (UTC)[reply]
Sort of. Obviously making microwaves then converting them back to electricity would use more energy than it would produce. However, special metallic foils are used under food to absorb microwaves and turn them into heat, to toast the food from underneath. StuRat (talk) 03:45, 21 July 2008 (UTC)[reply]
There are also various plans (and when I say plans, I mean vague ideas that may or may not have had a 1/10,000 scale prototype made so far) to do things like power spacecraft with microwave lasers, or use microwaves to "transmit" electricity without wires - see microwave power transmission. Confusing Manifestation(Say hi!) 04:16, 21 July 2008 (UTC)[reply]
But a simpler answer to the question of whether we have technology taking advantage of this effect is the antenna used by every radio receiver, every TV set not connected to a cable system, every satellite dish, and so on. Without it, radio and TV broadcasting would be impossible. --Anonymous, 04:21 UTC, July 21, 2008.
As for why foods taste different, there are many reasons. One is that the air doesn't heat up in a microwave oven like in a regular oven. This means the surface of bread doesn't dry out, for example. That's good if the bread was stale already but not so good if it was soggy. Another diff is that foods often cook for different lengths of time. Longer times allow flavors to blend more. StuRat (talk) 03:31, 21 July 2008 (UTC)[reply]
There are some interesting experiments with microwave ovens which I have seen on You Tube that take advantage of the fact that when a match is lit and covered with a glass inside a microwave the burning gases act like a conductor. Placed in a microwave oven the microwaves then react with burning gasses to form a plasma in a very spectacular fashion. -- adaptron (talk) 07:28, 21 July 2008 (UTC)[reply]
One of the reasons why food tastes different is the lack of 'browning' - microwave ovens use a lot of quite low energy waves - (lower energy than that given off by a heat lamp) - but uses massive ammounts of them - it's a bit like cooking with massive amounts of tepid water (very poor analogy) - because the energy is low it does not cause burning/browning - a bit like steam cooking.
High energy cooking such as using a pan, or oven causes more chemical reactions to occur eg see Caramelization, also maybe look at Maillard_reaction - these reactions cause a change in constitution that gives a different taste.
Here is an article detailing the reason microwaved foods taste different. According the to webpage, the temperatures and cooking times involved in microwaving are insufficient for the Millard reaction to occur. Because of this, foods cooked in conventional ovens have greater quantities of volatiles associated with pleasant flavours and less undesirable substances. --Bowlhover (talk) 07:19, 22 July 2008 (UTC)[reply]
Does any article describe or point to a reference of an experiment in which a large diameter axial fan was setup in the vertical and turned at high speed for the purpose of generating a vortex to serve as a typhoon or a hurricane "seed"? -- adaptron (talk) 07:21, 21 July 2008 (UTC)[reply]
Well, a hurricane is out of the question. Their spin is a consequence of the Coriolis effect, not a requirement for formation -- much less issues of scale. A vertical fan is also the wrong method of formation for a tornado, which originate from horizontally-inclined mesocyclones. Of course, the incorrectness of the approach doesn't preclude somebody from conducting an experiment anyway. 199.209.144.218 (talk) 12:43, 21 July 2008 (UTC)[reply]
Skin Bleaching
Started to read a new trend of anal bleaching but was not able to locate any legitimate medical articles on the procedure and the safety of this. Does anyone have any info or links for me? I don't know exactly what chemicals are used or any long term effects of this? .....you can start laughing now..... --JennaHunter (talk) 13:15, 21 July 2008 (UTC)[reply]
I would certainly expect it to be painful and result in swelling. I'd expect that fasting before the procedure might be in order to reduce the...err..."use" of the area following the procedure. Perhaps only bleaching a bit at a time might be safer, but whole area bleaching is probably done, too. StuRat (talk) 13:37, 21 July 2008 (UTC)[reply]
Definitely. Last week there was a report in German TV about a shop in China that offers the service. Of course, their formula is kept secret. --Ayacop (talk) 07:51, 22 July 2008 (UTC)[reply]
How about a tattoo instead. I suggest one on your butt cheeks that says "If you're close enough to see the color of my anal sphincter, you're too damn close !". StuRat (talk) 21:30, 21 July 2008 (UTC)[reply]
Depends on the context. If your talking about a global-view, then anything anything above the contentnal shelf... ~300feet. If your talking about a local ecological view then either (1.) anything above the thermocline (~30-50 feet) or (2.) anything in the zone where sun-light is a major factor (~150feet). Of inteses might be: Intertidal zone, Littoral zone and surf zone. 63.80.111.2 (talk) 17:30, 21 July 2008 (UTC)[reply]
General usage amongst geologists interested in modern and ancient sedimentary environments is that waters are shallow up to about 100m, but it doesn't seem to be something that is rigorously defined. Mostly shallow water is used for areas of the continental shelf as opposed to the continental slope or abyssal plain. Oceanographers may well take a different view. Mikenorton (talk) 17:38, 21 July 2008 (UTC)[reply]
Stability of bikes with different wheel-sizes
My father and one of his oldest friends have been debating an issue of physics ever since they where in their early teens. They both got bikes when they were 13 or 14 and they (naturally) started arguing which one was better. My father's bike had bigger wheels, so he argued that it's more stable. Since the wheel is bigger, the gyroscopic effect of the spinning should be bigger, my father thought. His friend, as young boys are want to do, passionately disagreed. He argued that if the bikes are travelling at the same speed, his wheels will spin faster, thus eliminating any advantage my fathers bike might have had. it's now 35 years later, and the issue still haven't been settled.
He asked me, and I told him only the very basic stuff I know, that the gyroscopic effect depends on the angular momentum of the wheel, which does increase with the size of the wheel. However, I haven't studied physics for years and years, and I can't even come close to figuring out whether the faster rotation of the smaller wheel will be enough to outweigh the longer radius of the larger wheel. I suspect this comes down to an issue of mass, since the larger wheel presumably have more mass, it will win out. But what if the two wheel had the same mass (the smaller one is denser, or something)?
I'd say the larger wheeled bike would have a greater rotational inertia, since that's related to the square of the radius, not just the radius. That, in turn should provide more gyroscopic effect. However, I disagree that the gyroscopic effect is all good. While it helps maintain stability while going straight, this also makes turns more difficult, requiring you to slow down more to turn. StuRat (talk) 16:57, 21 July 2008 (UTC)[reply]
The moment of inertia, according to StuRat, varies according to r2 - since the angular velocity in this circumstance varies according to 1/r, the larger wheeled bike will "win". --Random832 (contribs) 18:44, 21 July 2008 (UTC)[reply]
The larger-wheeled bike will be more gyro-stablilized. That doesn't mean it will be more stable -- gyro-stabilization is a fairly negligible contributor to keeping the bike upright. The more important number to look at is something called trail -- see the article Coneslayer pointed to. --Trovatore (talk) 20:50, 21 July 2008 (UTC)[reply]
A minor point to consider: IMO the moment of inertia should vary as r3, since we can probably assume the mass is concentrated at the circumference and the mass per unit length of the circumference is the same for both sizes of wheel. Therefore, m will vary linearly with r, so mr2 will behave, to within the approximations, like r3, so the larger wheel wins by more. —Preceding unsigned comment added by 91.143.188.103 (talk) 15:43, 22 July 2008 (UTC)[reply]
I'd say plain, air-popped popcorn with no toppings is an OK choice, based on the glycemic load of only 3 units per cup: [11] (out of around 100 units per day as a general recommendation, likely less for diabetics). Also, it's difficult to consume calories very quickly with such popcorn, so what little insulin production a person retains might be able to handle this slow pace. However, since a cup of popcorn only weighs 8 grams, it's easy to eat a dozen cups without even thinking about it. Such quantities would be bad. If this isn't just a general knowledge request, but pertains to a particular individual, I'd strongly suggest talking with a doctor or nutritionist recommended by the doctor. StuRat (talk) 17:15, 21 July 2008 (UTC)[reply]
Concur with StuRat, and, just to add something to this ec, I'll again emphasize plain, air-popped popcorn. Other varieties start loading up stuff that increase health concerns, diabetic or not. — Lomn17:25, 21 July 2008 (UTC)[reply]
I don't really recall pepper having any adverse health effects, so it should be addable to air-popped popcorn. But I'm not a doctor, and you really should consult an expert. --Wirbelwindヴィルヴェルヴィント (talk) 17:41, 21 July 2008 (UTC)[reply]
IF A TYPE 2 DIABETIC EATS A LOT OF ANY SORT OF POPCORN IT WILL CAUSE VERY HIGH BLOOD SUGAR, GUARANTEED. HIGH BLOOD SUGAR IS VERY UNHEALTHY. Edison (talk) 04:27, 22 July 2008 (UTC)[reply]
That's true if measured in mass, but not in volume. Since popcorn has such a low density, you can eat a fair volume (say a cup of plain popcorn), without having much effect on blood sugar. StuRat (talk) 07:12, 23 July 2008 (UTC)[reply]
Fan blades and turbine blades
Why are fan blades and wind turbine blades generally very different shapes? Fan blades (such as from a desk fan) are frequently much larger and more "dish" shaped that turbine blades, which are usually thinner and more wing-like.
I would have thought that if both designs were aimed at maximizing efficiency, where efficiency is either most wind per Watt or most Watts per wind, that the two blades would look quite similar. No? — Sam 17:20, 21 July 2008 (UTC)
They are used in different ways. See turbine for more details about why they are shaped the way they are. Also, when your dealing with a desk-fan, the efficiency is much less important then a turbine. ---J.S (T/C/WRE) 17:33, 21 July 2008 (UTC)[reply]
There are two issues with "efficiency". In one case (a desk fan), the most efficient fan is the one which can be produced in mass quantities, very cheaply, and complete the job of moving enough air to make the user feel good. In a wind turbine, the most efficient turbine is the one which moves the most amount of air using the least amount of power (or produces the most amount power given some standard amount of wind). As such, a desk fan usually has blades that are cheaply cut out of sheet metal and cheaply formed into a scoop on a mechanical press. A turbine will use much better materials and designs. -- kainaw™17:37, 21 July 2008 (UTC)[reply]
Seeing as no one has explicity said it - a fan blade and a turbine blade that operate under the same conditions should/could be exactly the same shape.
Turbine blades may be thin because they operate under extreme conditions and so need to be flaw free.. making a continuous fan shape flaw free is harder than making a lot of smaller blades flaw free.
Also using a lot of blades allows the depth of the fan to be reduced - a continuous blade would have more depth - this may be important in enclosed things.
Interestingly the turbines in water generation plants are much more like fans than their counterparts in gas turbines/jet engines eg see Francis turbine, here you might be able to guess why a single piece turbine is favourable (or just easier) over a multibladed one. I particularily like these images: (Note however that this type of turbine does have linear flow, it's centrifugal..)87.102.86.73 (talk) 18:51, 21 July 2008 (UTC)[reply]
Oh in that case one of the factors is also that in a fan the air is started from almost zero velocity, and it doesn't have to surive high winds.. Also such a fan could not have the pitch of the blades easily altered. For a wind turbine the opposite is true - the air/wind can be many speeds and so it is useful if the pitch of the blades can be altered - this is easier with narrow blades, it is still possible with thicker blades - but these will also cause more force on the turbine support in high wind - there's a safe limit at how much sideways force can be put up with on the turbine support.
I think it's easier to see why a typical fan would be totallly unsuitable for high winds, rather than explaining exactly why the wind turbines have blades of a certain dimension.87.102.86.73 (talk) 19:11, 21 July 2008 (UTC)[reply]
Fan blades are not the shape they are just because the shape is cheap to make. Aerodynamic studies in the 1930s, for starters, led to redesign to reduce the noise they made. The basic shape of the individual blades was altered and noise was reduced. I am sure that the science of fan making has continued apace to get the most air moved as quietly as possible for the least energy charge, beside the cost of fabrication. Edison (talk) 19:12, 21 July 2008 (UTC)[reply]
Also the long thin shape of wind turbine blades is less succeptable to cross winds than and smaller thicker design. And house fans need to be compact, so a long thin design is impractable.87.102.86.73 (talk) 19:41, 21 July 2008 (UTC)[reply]
Thank you all very much for the great answers! Here's what I'm taking away, correct me if I've misunderstood: Under the exact same conditions, what would be efficient for a fan would also be efficient for a wind turbine. However, 1) The conditions are not the same, and 2) efficiency is not the only factor, and is of much lower importance for desk fans than for turbines. — Sam 20:10, 22 July 2008 (UTC) —Preceding unsigned comment added by 63.138.152.238 (talk)
Recycling, is it a stupid thing to do?
I recently watched an episode of bullshit on recycling and they said it was more expensive and also more environmentally destructive, do you have any data about it? 88.203.106.28 (talk) 19:56, 21 July 2008 (UTC)[reply]
Did you look at the recycling article? It would be interesting to know what examples were given in the show you saw. Recycling#Criticism offers some examples of dubious benefits.
It's cost effective and more environmentally friendly to recycle aluminum cans to obtain aluminum than to mine and smelt aluminum ore to get the same material. Same is true for paper; in fact paper mills recycle their own cuttings when trimming the sheets to size, because it's already paper, not wood pulp that needs mashing and bleaching. The list goes on; it's easier to get glass from other glass than to process raw sand to get glass. Generally, if you need a material and must either make it from raw materials (including the effort needed to mine the raw materials), it's environmentally and financially sound to get what you want from materials that have already been made.
Mind you, there are misguided environmental practices out there. Making ethanol from corn comes to mind as a particularly wasteful practice that consumes more energy than it produces. But that isn't really a recycling issue. ~Amatulić (talk) 20:04, 21 July 2008 (UTC)[reply]
Yes, although the studies showing greater than 1:1 efficiency seem to rely on accounting tricks. Nevertheless, perhaps I should have said instead that corn is one of the least efficient sources of ethanol compared to other sources. ~Amatulić (talk) 21:30, 21 July 2008 (UTC)[reply]
I'd say it would depend on what is being recycled and how. Probably the most efficient recycling is composting rotten food to make good soil. All that is required here is to separate out the rotten food, dump it in a pit, and leave it to rot. There are some other things that can be done to speed up the process, like introducing bacteria, worms, and water, stirring the contents periodically, and venting off gases to keep it cool. Since the methane recovered also has value, this can all be done quite cheaply. The least efficienct recycling may be on small electronic devices which must be manually broken down into different components and separated, at great cost, only to produce tiny quantities of reusable material. StuRat (talk) 21:21, 21 July 2008 (UTC)[reply]
I've read that recycling glass actually does not work out to have an environmental benefit. I can't back that up with science or citations, but I find it plausible. Apparently you need the same amount of energy to remelt glass as you do to make it. Then you have to add in sorting out the trash that comes in with the recycling and the fuel for the truck that drives around to every house picking it up. Of course this neglects that fact that recycling diverts glass from landfills. ike9898 (talk) 22:06, 21 July 2008 (UTC)[reply]
Hmm, Glass recycling contradicts that, as do the sources it uses, and stuff like [12]. So well, meh. But it certainly can be the case that recycling can be uneconomic. I hear plastics recycling is supposed more dubious, though again I can't back that up with science or citations, but I find it plausible. ;) --Fangz (talk) 22:30, 21 July 2008 (UTC)[reply]
It does depend. Recycling glass in the process-engineering sense of recycling is a pretty fantastic thing to do, and one of the best examples is milk bottles if you've got a milkman. The bottles go round and round the system with only a little cleaning required, and this is efficient in terms of energy and raw materials, as well as avoiding sending waste to increasingly unavailable landfill. This is called 'reuse' in lay-speak. Generally 'reusing' things in this way is very good. If the glass has been seperated by colour, and you have someone willing to use the product, then melting broken glass down and making it into new things is also pretty good, but not nearly as good as just using jars and bottles again as jars and bottles. This is reusing the glass, but is referred to as 'recycling' in lay-speak. Not nearly so good is if you've been given a load of different types and colours of glass, some of it broken, and told to deal with it cheaply in a way that doesn't involve landfill. So you crush it down into aggragate and try to sell it to be used as decorative covering for the ground. This takes something which a lot of energy has gone into making into jars and bottles and turns out glass gravel. So these things all depend. 79.66.124.253 (talk) 17:17, 22 July 2008 (UTC)[reply]
I wonder if instead of newspapers and bottles, it wouldn't be better to have curb-side recycling of items like batteries, and electronics, and fluorescent light bulbs. ie: Things are laden with chemicals we'd rather not have in landfills. APL (talk) 02:31, 22 July 2008 (UTC)[reply]
Here in Bermuda we aren't big enough to support our own recycling plant. We have to ship our recyclables across the Atlantic Ocean to foreign recycling plants. I really have to question whether it is worth it. PlasticupT/C16:35, 22 July 2008 (UTC)[reply]
When figuring out the economic cost-benefit ratios of recycling one should remember to take into account the long-term costs involved with raw material extraction (mining, logging, etc). The costs involved are not only the short-term direct cost to the company doing the extraction, but long-term environmental costs. The latter costs are often ignored in cost-benefit calculations, but over time can, in many cases, grow to large amounts, and frequently after the company that did the extraction and environmental damage no longer exists or is bankrupt, leaving the costs to be paid for by the public. Aluminum is a great example. The cost of cleaning up bankrupt aluminum smelter sites in the US, paid for by taxpayers, is enormous. So don't forget to add such things to the cost side of calculation. Pfly (talk) 07:15, 23 July 2008 (UTC)[reply]
Lifecycle assessment is something we need an article on. Maybe next week... Another thing that's important to bear in mind is what you do with something if you don't recycle it. Certainly in the UK we are physically running out of landfill, so you have to find something to do with your waste. 79.66.124.253 (talk) 19:26, 23 July 2008 (UTC)[reply]
Sugar water wine
Is it true that one can make wine out of refined sugar and water? I'm not supposing that the result would be any good, I'm just wondering if it would be wine.
In my view, no, because it's not made from fruit. (I don't consider sake to be wine, either.) But it's all in how you use the word, I suppose. --Trovatore (talk) 20:32, 21 July 2008 (UTC)[reply]
Not just those two things, no. There needs to be some yeast or other microbes to digest the sugar, and they will need more than just sugar and water to live on, as they can't grow and reproduce without a few other things. Then there is always the question of whether an alcoholic beverage qualifies as "wine" or not. StuRat (talk) 21:11, 21 July 2008 (UTC)[reply]
I assume the OP assumed the use of yeast. The answer is yes, you can make a semblace of "wine" from sugar water and yeast. Try it. That's basically how rum starts out. Or mead in the case of fermenting honey and water. In most western countries it wouldn't qualify as a "wine" but in other countries such as China, the term "wine" has much broader application, and your fermented sugar water would qualify. ~Amatulić (talk) 21:17, 21 July 2008 (UTC)[reply]
If it was relatively pure sugar and water, the yeast would peter out very quickly. They certainly need a nitrogen source and some trace minerals. There would be a little of these carried over in the yeast innoculum, but not enough. ike9898 (talk) 22:02, 21 July 2008 (UTC)[reply]
Perhaps not enough to ferment the wine to completion, but enough to make an unstable, low alcohol sugary wine, yes. If the use of the word "wine" is not legally regulated in your jurisdiction to require the use of grapes (EU). Rmhermen (talk) 23:00, 21 July 2008 (UTC)[reply]
There's a traditional Finnish alcoholic beverage called kilju that's made with sugar, water and yeast, manufactured mostly by teenagers (in secret, naturally) and serious-minded career drinkers conscious of the constant economic pressures they face. Copious vomiting and crapping yourself are only some of the benefits bestowed by this wonderful drink that is usually miraculously foul-tasting. I heartily recommend it to any and all who feel that there just isn't enough embarrassment and diarrhea in their lives. -- Captain Disdain (talk) 08:21, 22 July 2008 (UTC)[reply]
Current wind farms show a very small percentage (1%?) of the rotational area being used to generate energy at any time - is there a reason for this? (is noise a factor?)87.102.86.73 (talk) 20:59, 21 July 2008 (UTC)[reply]
Seems to me like 1% is about the ratio of blade area to rotational disc area. In that case, you may as well ask why airplane propellers use such a small fraction of the disc area for thrust? The answer is likely the same: the additional mass and drag from adding more blades has diminishing returns after a point. It's the aspect ratio of the blade that matters to get the most thrust for the least mass and drag. ~Amatulić (talk) 21:22, 21 July 2008 (UTC)[reply]
Depends on the application; a fanjet's thrust turbine uses 100% of the disc it occupies (i.e. when looking directly at the disc, there are almost no open spaces between the blades). Apparently a higher ratio can be efficient, and the efficiency may depend on the air speed required. Wind turbines and most airplane propellers are comparitively low speed, so mass and drag become important factors. ~Amatulić (talk) 21:33, 21 July 2008 (UTC)[reply]
J.S. : Ok, I'll play your mind game. Here is a photograph of a propeller that uses all 100% of it's circular disk area. [13] While far from ideal for this application, surely you're not suggesting that it would be worthless for power generation in a strong enough wind? APL (talk) 02:26, 22 July 2008 (UTC)[reply]
Similar to a thread above - don't confuse pushing air (or water in re the propeller) with drawing power from air. The two are not symmetrical operations. In the case of the pictured propeller, the Reynolds number will be dramatically different between air and water, so even operation as a propeller could not be expected as equivalent.
And in any case, I think (see thread approx. 1 month ago) that the primary consideration for space-filling on a wind turbine is the strength and cost of the bearings that have to support the load of the blades, and secondarily turbulence effects between the blades. Franamax (talk) 05:50, 22 July 2008 (UTC)[reply]
Cellular stuff usually involves absorbing something into the cell by osmosis. The insolubility of base carbon is likely unhelpful for that.--Fangz (talk) 22:49, 21 July 2008 (UTC)[reply]
Burned forests/shrub lands are an excellent source of charcoal. Certain plants are well adapted to growing post forest fire. Slash and burn agriculture is a perfect example of how charcoal can be used to enrich soils (though unusually done in an environmentally unfriendly manner). I can't think of anything of the top of my head that uses charcoal/hydrocarbons as a primary energy source, though if there are any, they would probably be one of those extremophile-bacteria types. 71.77.4.75 (talk) 01:29, 22 July 2008 (UTC)[reply]
Does charred wood from a forest fire count as charcoal? The key feature with producing charcoal is that it's done in the absence of oxygen. I would expect there's plenty of oxygen available during a forest fire, although I don't know for sure. --Tango (talk) 01:48, 22 July 2008 (UTC)[reply]
Yes, there would be a vast natural source of charcoal - forest fires. Within the fire zone and at the unburnt depth of any tree in the fire, there will be high heat and zero oxygen. Terra preta soil is enriched in charcoal (manmade) and provides high fertility, however the charcoal itself doesn't actually provide a source of either carbon or energy (since the carbon levels persist). Rather the charcoal provides a useful medium for growth of beneficial micro-organisms. Per Fangz, the problem would seem to be the insolubility of carbon in charcoal form. This is perhaps mirrored in the wide use that humans make of charcoal to filter everyting else, it is fairly inert. I don't know of any life form that can directly metabolize charcoal. Franamax (talk) 02:01, 22 July 2008 (UTC)[reply]
If you google for coal eating bacteria you'll get a lot of hits, I also remember an article where it was found that abandoned coal mines surprisingly released methane constantly due to those archaea. Of course, they would be able to digest charcoal, too, wouldn't they? --Ayacop (talk) 07:35, 22 July 2008 (UTC)[reply]
Cute, but I don't think that's what the OP is looking for. Technically, most of us use carbon as an "energy source" beyond our gas grills: think power plants. I think the OP wants to know what organisms break down elemental carbon as food. I think Ayacop got it with bacteria and archaea. --Shaggorama (talk) 14:35, 22 July 2008 (UTC)[reply]
Just to clarify, coal and charcoal are more than just carbon. Reading this news release tells me the bacteria are processing the complex molecules in coal, and not the carbon. In fact the (rather non-scientific) article implies they use oil as their nutrient source, and break down impurities as a side effect.-84user (talk) 15:29, 22 July 2008 (UTC)[reply]
OP here. It seems to me that insolubility is an unsatisfying answer. Some fungi do very well on insoluble cellulose; they enzymatically break it into soluble pieces. On a different subject, I think that microorganisms that can use petroleum as an energy source are known. Can anyone say anything about the carbon containing molecules in charcoal that would be relevant to their non-bioavailability? Thx ike9898 (talk) 17:32, 22 July 2008 (UTC)[reply]
But the ubiquity of cellulose in e.g. plant cell walls means there are strong evolutionary pressures to adapt methods of breaking it down. Carbon in charcoal, which I think is mostly in the form of graphite, is not so common. So the ability to break it down should be rare. Though as others have said, probably some bacteria do have that capability.--Fangz (talk) 23:30, 22 July 2008 (UTC)[reply]
One of the joys of having a young child is attempting to field their damnably simple questions. I've gone through the blue sky, the twinkling stars, how tires get made, and what that bug was doing to that other bug, but I'm stumped tonight. What is the most "apparently bright" thing to be seen in the world? We were experimenting with a magnifying glass on a clear sunny day and the question came up if the sun was the brightest thing in the world (yeah, I know, but if it's in the sky, it's part of the world as far as she's concerned...). Now, I don't want to get into quasars and absolute magnitude because that's not what she's looking for. Is there any light she could experience that is brighter than the sun on a clear day? Searches online come up with some interesting homemade flashlights, but they don't specify how bright they are compared to the sun. Matt Deres (talk) 01:26, 22 July 2008 (UTC)[reply]
Since people sometimes use welder's helments to view solar eclipses, I'd guess a welding arc and the sun have similar brightness (not that I'd make any recommendations about how to view an eclipse, I'm no expert.) In both cases, UV light is a significant aspect of the problem. --Gerry Ashton (talk) 01:42, 22 July 2008 (UTC)[reply]
Some types of arc welding are a good deal brighter than the sun. But that probably doesn't help you, you're not likely to buy an arc welder just for this, and it's not really safe to 'experience' up close anyway.
I think there are some lights designed for film-making that are available pretty cheap that are brighter than the sun at close range. Actually, I'll bet that at close range many photographic flashes appear brighter than the sun. A photographic flash would at least have the virtue be easy and relatively safe to demonstrate. Might be seen as a cop-out, though. APL (talk) 02:20, 22 July 2008 (UTC)[reply]
I'd go with a really powerful laser. The amount of light produced isn't all that much, certainly less than a nuclear flash, but if you point it straight at her eye, I imagine far more light would hit her retina than from a nuclear flash. I wouldn't demonstrate that one either, though! --Tango (talk) 01:45, 22 July 2008 (UTC)[reply]
Apparent brightness varies dramatically with distance. While our distance to the Sun won't vary all that much, I'd expect any rather bright light to appear brighter than the Sun if you put your eyeball right up to it (not recommended for those who wish to keep their vision). Some particularly bright lights would be search lights. A specific case is the spotlights pointing upwards from the Luxor casino in Las Vegas, which are bright enough to see from 275 miles away. I'd expect that your eyeball would explode from the heat if you put it right up to those lights. StuRat (talk) 01:47, 22 July 2008 (UTC)[reply]
All the examples above will suffice as more "apparently bright". Are you just talking visually bright? You might explain spectrum and point out how the sun can burn every part of your body within about 15 minutes - that's pretty hard to beat.
And when you're talking about what's brighter - I hope and am absolutely sure you've explained that we never, never look right at the sun to see how bright it is. The brightness of the sun itself is already past the scale where you only see how bright it is once, so that's the very most important lesson. I'm sure you've explained that, it's worth saying again!
And that said, as far as a light source where you can see ambient light, unlike a laser (any of which can also easily destroy your vision if viewed directly, but cast no ambient light) - an arc-welding flare is a good demonstration of a very bright light cast all around (again, never look at the arc!) and is impressive indoors; a film-projector bulb; a spotlight. Now take anyone of those, look near them in broad daylight - do you see a difference? Likely not. The sun pretty much rules them all.signed byFranamax (talk) 02:56, 22 July 2008 (UTC)[reply]
Lightning flash possibly? I know from experience that burning magnesium wire outdoors (so my eyes were already light adjusted) can be bright enough that I can't look at it directly. 71.77.4.75 (talk) 02:33, 22 July 2008 (UTC)[reply]
Those are both good, but if we agree that the sun is bright enough that we can't look at it directly, I interpret this question as "what makes other things look brighter than they do in broad daylight?" Perhaps the best test of this then would be - will this other light source cast a shadow behind something in broad daylight? So if I shine the searchlight or burn the magnesium on one side of a car, without (!) looking at the light source, but just looking at the car, at noon on a clear day, will I see a shadow being cast? Is that a realistic criterion? Franamax (talk) 03:07, 22 July 2008 (UTC)[reply]
That makes sense but again distance seems to make it more complicated. I don't remember the shadows clearly but I am pretty sure the light from the burning magnesium was powerful enough at close range to overpower a shadow cast by the sun in broad daylight. I tried to find some videos of burning magnesium in broad daylight. Here is a video of a small ribbon burning (it's enough to cause the auto brightness-senser of the camera to dim). Here is a contains-mild-swearing video of a bunch of adventurous gentlemen burning quite a bit of magnesium in an outdoor oven in midday. 71.77.4.75 (talk) 03:32, 22 July 2008 (UTC)[reply]
My thing is not "does it fill in the sun-shadow?", it's more like "does it cast a shadow the other way?" - but we may be talking about the same thing. There's no indication of that in the video by the league of gentleman adventurers, but they missed out on the fact that piping a feed of pure oxygen into the centre of their little pyro-fest would have dramatically enhanced it. If they'd used a little pure O2 in fact, they might have been able to incorporate ambulances into the footage :)
You're right about distance, as are all the above - but the OP is looking for answers for his little girl, and has ruled out distance via quasars not being applicable (and I'd say gamma ray bursters anyway). However I'd say Mg in O2, arc welding and possibly plasma torch welding would be the most accessible real-life demonstrations of comparable light sources. Now compare that with the fact that from 93 million miles away it takes the Sun a half hour to send you to bed feeling bad all over. (Leaving aside nuclear devices, which are best left unexplained until after the talk about sex - at least you can give a realistic reason for the purpose of sex) Franamax (talk) 05:20, 22 July 2008 (UTC)[reply]
I don't understand the need to be secretive about the purpose of nuclear weapons. People sometimes don't like each other and they fight to kill. I certainly knew that years before I was taught the details of sex. --Bowlhover (talk) 06:52, 22 July 2008 (UTC)[reply]
Just on the surface, that's a difficult subject for a child - 'cause the natural next question is "will someone try to kill me?". But you miss the major benefit of nuclear weapons - it's not to kill, it's to cause massive numbers of hideously wounded casualties, which tie down the resources of the defending power. Sit your young child down and read her Hiroshima by John Hersey. Explain to her how a fallout cloud would make her own hair fall out and how long it would take 'til she started vomiting and trace out on her face where the flesh would be melted to the bone. Were you taught those details when you were seven years old? Franamax (talk) 07:22, 22 July 2008 (UTC)[reply]
I never claimed that every single detail about nuclear weapons should be taught to a seven-year-old. In fact, most educated adults don't know how long it would take for nuclear bombs to cause vomiting or exactly where a person's flesh would be melted to the bone. Telling a child that nuclear weapons are used for war, or even that they waste the enemy's resources by killing civilians, requires none of the details you mention. And come on, "will someone try to kill me?" Any form of crime is more of a disconcerting topic than war unless the child's country happens to be in a nuclear war, and you can't possibly say parents don't or shouldn't inform children about crime.
Besides, the major benefit of nuclear weapons isn't forcing the enemy to provide disaster relief. It's either intimidation, or destruction of the enemy's military, economy, AND civilian population, with a focus on the first. --Bowlhover (talk) 08:24, 22 July 2008 (UTC)[reply]
Just a note for any casual readers: Do not ever look directly at the Sun; do not ever look directly at a welding arc or plasma arc; do not ever look directly at a projection bulb, especially through a focussing lens; do not ever look at the direct output of a laser of any type; do not ever look at burning magnesium metal. Doing any of these for any significant length of time can cause permanent damage to your vision. In some cases, this can be as little as 1/10th of a second (in some cases less). Use appropriate eye protection. Read instructions, ask experts, take precautions. Don't try to experiment because of something you read on Wikipedia - please! Franamax (talk) 05:33, 22 July 2008 (UTC)[reply]
Note that looking at the Sun without optical aid rarely causes permanent eye damage (see Sun#Observation and_eye damage). Burning magnesium is, as I showed below, 1/29th as bright; it is also much smaller than the Sun in angular size. Since burning the metal is a common high school experiment and was done without goggles in my former school, I would be surprised if it's dangerous. --Bowlhover (talk) 06:52, 22 July 2008 (UTC)[reply]
It is dangerous, which is why you're told not to look at it directly. The thing is, looking at the sun or a magnesium flare will damage just a part of your retina each time, causing a small permenant area of blindness. Over time you can acquire more of these until it becomes noticable. Don't look directly at the sun, and don't look directly at burning magnesium. 79.66.124.253 (talk) 17:00, 22 July 2008 (UTC)[reply]
The brightest light source on Earth or elsewhere is the laser described here, which can output 10^22 watts per square centimetre for a tenth of a trillionth of a second.
The "brightness" of an object, by the most common understanding of the word, is the amount of light emitted per unit of angular area. As distance from a light source increases, both the light's intensity and the source's angular area decrease with the square of the distance. The result is that brightness, termed surface brightness in astronomy, does not depend on the amount of space between the source and the observer. The shadow test is thus inaccurate because it measures irradiation, not the power of light in one unit of angular area.
Burning magnesium is significantly dimmer than the surface of the Sun. According to its article, magnesium's combustion temperature is 2500 K. A calculation using the Stefan-Boltzmann law reveals the Sun's photosphere, at 5778 K, to be 29 times as bright. --Bowlhover (talk) 05:45, 22 July 2008 (UTC)[reply]
I guess the article discusss it but looking at the sun directly is usually does not cause permanent damage but can be particularly dangerous during an eclipse where the lack of ambient light means the pupil may not dilate sufficiently. It's also likely to be very dangerous if you have just be given something to dilate the pupil (causing mydriasis), e.g. as part of an eye test or have taken some drug (this includes atropine and amphetamines) or have a disease (e.g. Argyll Robertson pupils, Marcus Gunn pupil, Adie syndrome) or whatever resulting in the condition. All in all, while most people are probably not going to suffer damage from looking at the sun, it's still an incredibly bad idea IMHO. (Note that the reason looking at the sun is not usually dangerous is not because it isn't bright enough to cause damage, it most definitely is, but because your pupils constrict in the bright daylight so don't allow enough light in to cause permanent damage. Also bear in mind that your unlikely to know your eyes are being damaged until it's way too late.) As for burning magnesium, I don't know that much but our own article Magnesium says it's dangerous. My guess is that it can be dangerous particularly if you are close to it, it's a significant amount and lasts a long time. From what I can recall when I was in school, this tended to be a short experiment (under 10 seconds), was usually done by the teahcer (i.e. you were probably resonably far away) and wasn't a great quantity (=smallish flame) likely greatly reducing the risk of harm. I don't see the fact that it's 1/29 as bright as the sun if true as significant as I mentioned already the sun is already way bright enough to damage your eyes. Also from what I can tell the amount of UV light is important too. Nil Einne (talk) 13:29, 22 July 2008 (UTC)[reply]
Wow, lots of replies! Thanks guys. Nothing like a six year old's question to get the smart folks thinking. There's a couple of really good suggestions here. The 'cast a shadow' thing sounds like a good one to try, at least to explore the topic (which is probably more important than the answer, even there even is one). The one problem is that I'm not sure it's actually correct. Lots of things can cast opposing shadows on a clear day, even regular flashlights. Maybe I should ignore my own restriction above and try explaining the difference between apparent and absolute magnitude, etc. Less viscerally satisfying, but still good to know.
And as for the questions above, she's already aware of her mortality and we've already stayed up a few nights having very impromptu discussions about it. We haven't talked about nuclear war, but she knows about soldiers and war, etc. at least in general, historical sort of sense (Remembrance Day and all). We haven't had an in-depth sex talk yet, but she knows mom and dad somehow put her together inside mom ;-). I try to answer questions on the level they're asked, but I've always felt that if she wants to know, it's my duty to inform her, even if its unpleasant or uncomfortable. Matt Deres (talk) 10:55, 22 July 2008 (UTC)[reply]
Going the other way, you can use the shadow trick to show that an incandescent light bulb is less bright than the sun. On a clear day, you can see the shadow of the filament of a (clear) incandescent light bulb even when the bulb is lit. (But a laser still has higher intensity than unfocused sunlght.) Your daughter is already aware that focused sunlight is more intense ("brighter") than unfocused sunlight. -Arch dude (talk) 13:07, 22 July 2008 (UTC)[reply]
I have no source for this, but I'd suggest the experience of a strobe light in the dark being the brightest light you could let your daughter safely experience. The contrast from low light to intense flash can be blinding: let her eyes adjust to the dark and give a sudden strobe flash, see what happens. The brightest man made light I can think of (short of a nuke) is the arc on a plasma torch, which can cause severe damage to the retina. --Shaggorama (talk) 14:31, 22 July 2008 (UTC)[reply]
Hi. As an aside question, how bright would say, the Hiroshima bomb be in apparent magnitude from say 10km? Thanks. ~AH1(TCU)18:34, 22 July 2008 (UTC)[reply]
Still, you'd probably be close enough to test for yourself whether you really *can* see the bone structure of your hands through your flesh in the light of the flash. In the seconds before your eyes stopped working permanently. --Kurt Shaped Box (talk) 21:32, 22 July 2008 (UTC)[reply]
So, how did a butterfly end up being named 'Common Gull'?
Quite a few of the butterflies in the genus Cepora seem to include "gull" as part of their common name. [16] I bet the word "Gull" is being used in another sense, perhaps an obsolete definition, place name, or proper name. I tried looking up "cepora" and "nerissa" in latin and greek but came up blank. I thought of the word "Gules" used in heraldry for red but the butterflies of the genus seem to be mostly yellow or white. That still doesn't exclude the possibility of "Gull" being a corruption from another language. I'll think about it some more... 71.77.4.75 (talk) 02:56, 22 July 2008 (UTC)[reply]
I got a potential origin idea. From what I can make of using online translators, the word "gul" in Hindi either is or is the first syllable of the word for rose or flower (gulAba?). Someone fluent in Hindi please check me on this. These butterflies seem to be common in India so the connection between the Indian word for flower/rose and the butterfly makes a bit of sense. 71.77.4.75 (talk) 03:08, 22 July 2008 (UTC)[reply]
You might have more luck on the language desk, but among the several meanings of gull in the OED is an obsolete adjective meaning "yellow, pale", from the Old Norse (gul-r), Swedish and Danish (gul).--Shantavira|feed me06:33, 22 July 2008 (UTC)[reply]
Do We Reduced Brain Power (Energy Save Mode like a laptop)
When I was struggling to get to sleep last night a thought occured to me. My laptop has 'energy save' mode - and in order to maximise battery-life it does a variety of things, one of which is 'turn-off' some of the processing power (perhaps by only using one of the 'cores') - this prolongs battery-life and allows functioning it a less energy intensive rate. My question is this...Does the human-brain do this ever? Given a time of low-food intake would the brain start 'shutting down' non-essential processing so as to reduce energy use. Would your IQ drop if sufficiently starved of energy (not to the point of no energy of course)? And does the act of thinking consume much more energy than not thinking? E.g. If I sit trying to work out a complicated calculation in my head does it consume more energy than just sitting idly doing nothing? Sorry if this is a daft question but I was struggling to sleep and it then (of course) consumed my thoughts for a while. The thing i'm thinking is they say hunger affects concentration - is this because the brain is working in 'best battery performance' rather than 'best performance' mode (to use my laptop's setting selections)? 194.221.133.226 (talk) 08:07, 22 July 2008 (UTC)[reply]
Not knowing exactly how much calories is used by the brain I recall there is no Save Mode for brain activity---it's just that your consciousness varies. We know now better than the Hubbard propaganda that suggested the amount of activity coincides with consciousness or even IQ. Also, the brain gets always the most blood, i.e., when your brain starves the other organs were already starving for some time. Of course I'm simplifying with this but that's the picture. --Ayacop (talk) 09:15, 22 July 2008 (UTC)[reply]
Everything you said was correct. The brain does conserve energy during times of starvation (which can include diets), it does use a substantial part of the energy your body uses, and it does use more during mentally challenging activities (like spelling, in my case). StuRat (talk) 13:49, 22 July 2008 (UTC)[reply]
Also note that the "nonessential functions" the brain shuts down are sometimes esential after all, such as when operating a vehicle or heavy machinery, where "brain fog" can be fatal. StuRat (talk) 13:53, 22 July 2008 (UTC)[reply]
I've seen a ref (can't find it now) to the effect that intense mental activity actually increases the carbs burned by the body. I wonder if thermal imaging would show the brain running hotter when doing complicated calculations or memorization, recall, puzzle solving, and such pursuits, compared to just sitting and not thinking about much in particular or in light sleep? Edison (talk) 23:57, 22 July 2008 (UTC)[reply]
Not thermal imaging, no, because blood quickly removes the excess heat generated. However, there is a process where radioactive glucose is given to the patient and the more radioactive portions of the brain show where increased brain activity uses more glucose. (I don't think I'll be personally volunteering to have my brain irradiated, however.) StuRat (talk) 07:05, 23 July 2008 (UTC)[reply]
Boiling Water at a different tempreture to its boiling point.
You can even boil water at room temp by putting it in a sealed syringe and pulling back on the plunger to lower the pressure. StuRat (talk) 13:44, 22 July 2008 (UTC)[reply]
Is it definitely boiling, as opposed to just having air forced through it (from around the plunger, into the syringe)? --Allen (talk) 17:08, 22 July 2008 (UTC)[reply]
Also look at how much gas volume is present when the plunger is pushed back in compared to how much gas bubbled when it was pulled back. DMacks (talk) 18:24, 22 July 2008 (UTC)[reply]
I'm just figuring that a good deal of air has to be getting around the syringe; otherwise they'd be creating a near-perfect vacuum in there, which I'd think one wouldn't be able to pull against so easily. --Allen (talk) 11:49, 23 July 2008 (UTC)[reply]
Normal air pressure is around 15 PSI, which would mean only 15 pounds to pull a one inch cross-sectional area syringe (a huge syringe) against a pure vacuum. StuRat (talk) 15:13, 23 July 2008 (UTC)[reply]
When the syringe barrel is pushed up, look at how much/little gas space there is: that's exactly how much air has leaked in during the experiment. Note that you cannot (even with a high-vacuum pump) get anything close to a "perfect" vacuum here. You will always have the vapor pressure of the water: as you try to reduce the pressure below the vapor pressure of water, the water vaporizes to keep the pressure at that point. That's exactly what boiling is:) DMacks (talk) 12:51, 23 July 2008 (UTC)[reply]
You can apply a vacuum pump to a properly constructed container with room temperature water in it and the water boils when the pressure gets low enough. You can even make ice this way. But the oil will need to be changed afterwards. In the 1960's a man testing a prototype American space suit was exposed to near-vacuum in a vacuum chamber when an air hose came loose, and he said the last thing he remembered before blacking out was the strange sensation of the saliva on his tongue boiling. He survived when the chamber was quickly repressurized.(edited to re-add the text the browser windo ate. It oftern happens that I insert text, everything looks fine in the edit window, then when I hit save some of it disappears). Edison (talk) 20:29, 22 July 2008 (UTC)[reply]
Yes, the article you cited describes the incident. I recently saw a documentary on TV which had the original film or video and audio of the incident. Edison (talk) 23:55, 22 July 2008 (UTC)[reply]
Named storm in Atlantic crossing over into Pacific
I am wondering if (a) has the following happened, and (b) if so, how the storm naming has been handled.
Aphasia only when alone? Or just refusing to talk to oneself?
If a person wants to say a sentence, but can't get the words out, when alone, but can when there is another person providing a stimulus, would this be aphasia, or would it just be a mental block against talking to oneself? In looking at the article on aphasia, it sounds like the disorder is mroe than just the ability to get words out, but on the other hand, intrapersonal communication implies that everyone talks to themselves - or at least has the physical capability to.
So, I guess what I'm getting at is, is aphasia only consistent speechlessness? Or, does there have to be more of a general language problem? Is it possible for a person to develop such a persistent mental block agsinst talking to oneself that they can't speak unless someone else is int he room? (It's just nice to know that it is normal to talk to myself :-) 209.244.187.155 (talk) 18:34, 22 July 2008 (UTC)[reply]
According to the article, aphasia is caused by brain damage, so it likely to be consistent. There are other conditions which may be relevant - for example there are children that will only talk to close family and friends and will go completely silent in public. I don't know what that's called, though. What you describe seems to be the opposite of that. --Tango (talk) 20:23, 22 July 2008 (UTC)[reply]
Sorry, but we cannot speculate about medical diagnoses here at the Reference Desk, per the guidelines posted at the top of the page. You might wish to discuss this with your physician. Edison (talk) 20:25, 22 July 2008 (UTC)[reply]
Find me Alexander Selkirk's physician and I'll ask him. :-) I had read where this real life castaway, who inspired somewhat the story of Robinson Crusoe, had mostly lost the ability to speak after being stranded for 4 years with no human companionship, and wondered if this would have been possible because he simply didn't exercise that while alone. That's where this question came from.
Although, ironically, I found the man's name in the Crusoe article, and read that a fall from a cliff is mentioned (fromt he talk section), which implies if he did lose it, it may have been because of a physical injury after all, and not because of some inhibition agains ttalking to himself that had grown into an inhibition agaisnt speaking, period, unless in the presence of others.
I thought my query would be a little less convoluted without throwing the stuff about Selkirk in there, and Crusoe - especially since I mention I can talk to myself so don't have this problem - but I guess not. And who knows, maybe what I read about Selkirk having lost the ability to speak was wrong, anyway.
Though, now that I look at your answer, Edison, you probably *did* understand it wasn't my problem and that I can talk to myselrf (and do). And, I can understand, perhaps it is best you don't speculate on anyone's medical condition. I imagine the condition of someone 300 years ago would lead to a much higher degree of speculation than you'd ever want to do Wikipedia, even without the legal ramifications. :-)
(And, I should add, now looking at the article on Selkirk that is cited, what I'd heard about his losing his ability to talk may have been quite incorrect anyway.)209.244.30.221 (talk) 21:18, 22 July 2008 (UTC)[reply]
Rodent identification
I'm trying to figure out what rodent I just saw in our garage. It was likely a chipmunk, but it looked too large to be so (though the light was off, so it's difficult to tell). Does anyone know how I can find out what rodent species are native to Manitoba? 24.76.161.28 (talk) 19:39, 22 July 2008 (UTC)[reply]
I believe this is a protective mechanism. Your body detects that it's overheating, and lowers your metabolic rate to limit heat production to fight this. Lowering your metabolic rate will result in you being sluggish and tired. StuRat (talk) 06:52, 23 July 2008 (UTC)[reply]
Hi. No, that doesn't work when it's humid, as shown by the above link. Sweating usually cools you down by evaporating, but when it's that humid, the sweat can't eveporate, so it just sits there, making you feel hotter. Hope this helps. Thanks. ~AH1(TCU)16:34, 23 July 2008 (UTC)[reply]
July 23
Theory of subspace model
Search for help on theory of subspace model!
'System identification: theory for the user'(2nd edition, 1999) had introduced such theory about subspace model in section 10.4. However, I cannot get that book. If possiable, please help me in finding some materials about that. Your kind help will be appreciated sincerely. —Preceding unsigned comment added by Cjt1982818 (talk • contribs) 01:44, 23 July 2008 (UTC)[reply]
I've never even known it could be a synonym. A hamburger for me is most likely the premade burger or perhaps the pattie but defintely not ground/mince meat. BTW, is ground ham actually common? Ground pork is but I've never heard of ground ham. Nil Einne (talk) 13:38, 23 July 2008 (UTC)[reply]
"Hamburger" has no etymological connection to "ham". It was originally a "hamburger steak", i.e. a steak made the way people in Hamburg make them. Similarly a "frankfurter" is a sausage of the kind they make in Frankfurt. I suppose "hamburger" can then by extension mean meat sold as suitable for making a hamburger. Minced (ground) pork is called "sausagemeat" in the UK; if you wanted to make sausages at home it would be the thing to choose. Itsmejudith (talk) 14:00, 23 July 2008 (UTC)[reply]
Pork mince is available labelled as such in every supermarket I've seen. Sausagemeat contains other ingredients such as rusk. It's not easy to link products, but you can browse here to see. AlmostReadytoFly (talk) 14:08, 23 July 2008 (UTC)[reply]
"Two great nations separated by a common language?" It's hard to imagine sausage made of rusk. On the U.S. side of the pond it is "ground beef" in the store, and might become a hamburger, meatloaf, meatballs, sloppy joe, tacos, or lasagna. One would not list "hamburger" as an ingredient in any of these foods. The repeated findings of E coli or other pathogens in groundbeef made in giant meat processing plants, where intestine contents from one processing mishap may be mixed in with hundreds of other cows in a given serving of ground beef, makes me avoid steak tartare, which was quite tasty back in the day of beef being locally ground. Ive never heard "minced" applied to meat. "Mincemeat" in the U.S usually contains no meat, except perhaps for fat. Edison (talk) 16:20, 23 July 2008 (UTC)[reply]
Unindent. Google finds thousands of entries for "ground ham". The few I checked were recipes using both ground ham and ground pork. Perhaps people grind their own ham at home - I can't remember ever seeing ground ham in the meat section. Although there is deviled ham. Rmhermen (talk) 18:05, 23 July 2008 (UTC)[reply]
You'll have to be much more specific than that. What do the scientific symbols look like? Can you post a sample of the graph? What's the title? Where did you see it? --Bowlhover (talk) 05:43, 23 July 2008 (UTC)[reply]
That was gonna be my guess also. I don't know why, but many of my students call any sort of organized display of information a "graph". DMacks (talk) 07:04, 23 July 2008 (UTC)[reply]
I suppose it's a bit like how if all you knew were horses, you'd refer to a Frisian cow as 'a fat, funny-shaped, black and white horse'. Or something. :) --Kurt Shaped Box (talk) 18:08, 23 July 2008 (UTC)[reply]
(ec) Schizophrenia can involve stereotyped speech patterns, as can Tourette Syndrome. Also see Echolalia for one specific type of verbal repetition. 12:53, 23 July 2008 (UTC)
Can it please be explained to me why Methotrexate is used alongside Folic Acid. My boyfriend has been prescribed 5mg of Methotrexate once per week, with 5mg of Folice Acid every other day of the week. How does the Folic Acid react with Methotrexate. What exactly does it do to help RA? thank you
Methotrexate is an antifolate drug. (I recommend reading these links) Reducing the amount of available folic acid is beneficial to patients with autoimmune diseases such as RA. However, we don't want to eliminate all folic acid as it is needed for cell division. So a supplement is given. This is a bit of a rushed introduction to a relatively complex topic but I hope it helps! Fribbler (talk) 14:06, 23 July 2008 (UTC)[reply]
mostly water
Since the human body is made mostly of water, is it possible for one to melt, and how would this be achieved? 'cause I know this one girl and I swear when ever she phones me or touches me I start to melt. —Preceding unsigned comment added by 193.115.175.247 (talk) 12:28, 23 July 2008 (UTC)[reply]
You know that ice (solid water) melts at 0 °C and that your body is much warmer than that. Therefore, any water in your body is already "melted". Physically anyway:) DMacks (talk) 12:48, 23 July 2008 (UTC)[reply]
(Insert voice of favorite American sitcom dad.) Awww, how cute. You're not melting; I think you've got puppy love. Known in American slang as a "crush" nowadays. Probably among your first; or, at least you feel different about this girl than any other you've felt; hence you're unsure what that feeling of "melting" is.
While we can't give medical advice, I will say this - if my theory is correct, then the first thing you should do is ask how she feels when she talks to you. It's okay if one feels something and the other doesn't right away, because those feelings aren't what's going to last; feelings come and go. Keep maintaining the friendship, and remember that that friendship should be the key to your relationship. Find out what she likes, and do fun stuff together. Maybe it'll last,a nd maybe it won't. But, I know one thing. That feeling can be pretty intense. But, it's fun, too. Just don't go too fast with any girl, okay? The key to a girl you like is, would you still like her if you were both really old, bald, and incontinent. but, it's okay to have fun and think about this situation now; because those feelings are real. It's part of gorwing up.
Boy, that *did* sound like a sitcom, huh? :-) Yes, that's the way I talk, too.
Oh, and to the original question, for something to melt it has to be at a very high heating point. So, for skin and bones to literally melt, you'd have to be in a blast furnace or something. Yes, the body is mostly water, but the part that isn't is very solid and rugged.Somebody or his brother (talk) 12:56, 23 July 2008 (UTC)[reply]
P.S.: Feel free to show her this response if you struggle for a topic of conversation, or how to approach your puppy love. It may help you talk about and emphasize the friendship part and also be good for a laugh, perhaps. Good luck.Somebody or his brother (talk) 13:20, 23 July 2008 (UTC)[reply]
The human body is made mostly of water in the same general way as a water balloon is. Ever seen a water balloon melt? — DanielLC17:10, 23 July 2008 (UTC)[reply]
Is there a Wikipedia article or other online reference that shows the yield of biochar, bio-oil and syngas from various types of municipal organic waste such as sludge and bio-mass? —Preceding unsigned comment added by Adaptron (talk • contribs) 15:59, 23 July 2008 (UTC)[reply]
The relevant articles are gasification and pyrolysis though I can't find any figures there - it probably also depends on the exact process used - which you could be more specific about.
How long humans can stay under water holding their breath? How long perl-collectors in Tahiti can hold their breath under water?
What is the world record of holding the breath?
Dimitar (medical student) —Preceding unsigned comment added by Velimir14 (talk • contribs) 16:40, 23 July 2008 (UTC)[reply]
Please help solve this mystery: water from a water filter turns slightly cloudy after boiling. The water is somewhat high in dissolved minerals. The filter is supposed to reduce a variety contaminants in the water, including lead. Before boiling, the filtered water is clear.
Could this not merely be lots and lots of tiny air bubbles? I know that the water from my hot tap sometimes comes out milky-white due to this. If I put some in a glass and leave it to settle, I can see the bubbles (quite slowly) rising to the top, with the water below clearing. --Kurt Shaped Box (talk) 18:44, 23 July 2008 (UTC)[reply]
Could it be water hardness coming out as a fine suspension after boiling - some sorts of hard water do this. Also are you sure it's not your heating device - have you tried boiling in a different thing - eg a very clean pan or dish?87.102.86.73 (talk) 19:05, 23 July 2008 (UTC)[reply]
Salmons - polyphyletic or paraphyletic?
Given that the common name "salmon" does not correspond exactly with any taxonomical group, and that some "salmon" species are closer to trouts than to other "salmons", should the term "salmon" be considered as:
a) a paraphyletic grouping
b) a polyphiletic grouping
c) a vernacular name with no corresponding taxonomical group (or groups)
I believe that C is correct. "A" might be correct if it was determined that the common ancestor to the group was a salmon and that trout form a monophyetic group that could be pruned from the tree (see paraphyly). "B" would only be correct if the term salmon included multiple monophyletic groups separated by other groups and I don't think that's the case (hence my qualifier at the beginning). Matt Deres (talk) 20:01, 23 July 2008 (UTC)[reply]
[edit conflict] I'd say C. To determine whether the group was paraphyletic or polyphyletic, you'd have to know whether the most recent common ancestor of all salmon was called a salmon. My guess would be that we don't know exactly what fish that was, and that we certainly haven't thought to decide whether it was a "salmon" or a "trout". --Allen (talk) 20:08, 23 July 2008 (UTC)[reply]
Is cortisone a patented form of cortisol?
I understand the drug companies pushed cortisone because of that, is that true?
Thanks Mathityahu (talk) 20:08, 23 July 2008 (UTC)[reply]
(Note however that this type of turbine does have linear flow, it's centrifugal..)87.102.86.73 (talk) 18:51, 21 July 2008 (UTC)
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