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.
one day i was working installing fences and i noticed a praying manits. it was the size of a male and it looked like a wasp. it had the body of a wasp up to the thorax and the arms neck and head of a praying mantis. ive been trying to find something online that looks like the one i saw and im starting to wonder if its a new species. let me know if you have any knowledge on this subject. thanks for taking the time to read this.
Is dopamine the only material to transmit "delight" feeling? Is dopamine only used for transmit this kind of feeling?
Then my main concern is, what is the meaning(from evolvement history point of view) of this kind of feeling? what's the advantage for animal with this kind of feeling? For amorism,then for reproduction(in fact I don't it the best way for breeding numerously, rapidly and widly)?
Aaadump (talk) 02:52, 12 July 2008 (UTC)aaadump[reply]
I don't know if dopamine is the only chemical that does this—in fact I doubt it. But the evolutionary reason for having a neurotransmitter that makes the organism happy should be pretty clear; it's the basis for a good deal of learned behavior, just as having a neurotransmitter for pain and discomfort would be valuable. See, for example, operant conditioning, and try to imagine how impossible it would be for a creature to actively learn if it didn't experience some sort of positive feeling at times. --98.217.8.46 (talk) 03:31, 12 July 2008 (UTC)[reply]
Dopamine isn't the only pleasure hormone; others include oxytocin and endorphins. Dopamine has a wide variety of functions other than transmitting positive feelings, as it plays a role in the cardiovascular system, regulating movement, learning, and information flow. See http://www.vitamins-supplements.org/hormones/dopamine.php for more details.
As for the evolutionary benefits of pleasure hormones, oxytocin is produced during labour, breastfeeding, and sex. Endorphins are secreted after tiring activities and orgasms. The advantages of mitigating pain or rewarding the organism in these instances are pretty clear. --Bowlhover (talk) 04:37, 12 July 2008 (UTC)[reply]
chronic eye infection
Are there post consequences (sorry, I can't/don't remember the scientific term/word/name) of chronic eye infection(s) analogous (such as) chronic ear infections lead to deafness?68.148.164.166 (talk) 05:32, 12 July 2008 (UTC)[reply]
See crown ether - 18crown6 forms a complex with potassium specifically which solublises that cation in organic solvents, this will make the potassium carbonate more soluble in acetone.87.102.86.73 (talk) 11:32, 12 July 2008 (UTC)[reply]
I am a bit confused by the description of this photograph [1]. The description claims that this photo shows ants and aphids, but I am not sure I see ants, or at least any species of ant I am familiar with. To me, I see aphids and something that looks like a beetle. Are those large black beetle-like things a type of ant?--Filll 14:45, 12. Jul. 2008 (CEST)
There may have been ants around, but possibly out of sight (cropped?). The view currently has in focus only aphid adults and nymphs. Shyamal (talk) 13:11, 12 July 2008 (UTC)[reply]
The description says, in German, "Aphids, who live symbiotically with ants" so I don't think it implies that there are ants in the picture. Fribbler (talk) 16:44, 12 July 2008 (UTC)[reply]
Tyre pressure
Is it true that the more a push bike's tyres are inflated, the less energy is required to propel the bike? If so why? -- SGBailey (talk) 13:23, 12 July 2008 (UTC)[reply]
Yes. Smaller area of contact with the ground, so less rolling resistance. Unless you massively overdo the inflation, I suppose, so that the tyres turn into huge balloons and the contact area increases again - but they would burst before that happened. --Heron (talk) 13:44, 12 July 2008 (UTC)[reply]
Not familiar with the term push bike, but searching through WP I found a picture of one. Doesn't look like you inflate the tires at all. For a regular old mountain bike or road bike, yes, the more you pump up the tires the easier it will pedal, but you have to balance it against reduced traction. A lot of times mountain bikers will keep their tires highly inflated until they get to the trailhead and then let a little air out, especially if they'll be descending. However running at too low a pressure is a good way to ruin your sidewall, as I found out (I didn't use to like to run high pressures because I got too many holes in my tubes that way). --Trovatore (talk) 16:46, 12 July 2008 (UTC)[reply]
If you just say "bike" the question of motor bike or push bike may be raised, hence the use of a distinguishing word. Your picture doesn't look like a push bike, but is instead a velocipede. -- SGBailey (talk) 21:04, 12 July 2008 (UTC)[reply]
Ah, so that would be one of those unnecessary back-formations where you disambiguate what's already the unmarked form. Along the lines of snow skiing or ice hockey or American football. --Trovatore (talk) 22:16, 12 July 2008 (UTC)[reply]
I'm not sure I understand what you are saying. In the UK at least there are bicycles and motorbikes. If you say bike, it is ambiguous; you either need to disambiguate or you need context. "Snow skiing" isn't a phrase I'm aware of. "Ice hockey" is similar in a way to "Field hockey" but is played on ice and the two games need to be distinguishable. I would imagine - though I don't know - that field hockey came first. "American football" obviously needs the disambiguation that it has since the game is completely different to "football" in the rest of the world - to disambiguate the other way one uses "soccer", but soccer is more of a nickname than the real name "football". I have no idea which came first, soccer or American football. Australian rules football is yet another different game needing its disambiguation. -- SGBailey (talk) 23:58, 12 July 2008 (UTC)[reply]
In the US we would call a "bike" a "bicycle" if we needed to distinguish it from a "motorcycle". The term "push bike" sounds weird to us, like a bike that doesn't work properly, so you must get off and push it home. StuRat (talk) 17:40, 13 July 2008 (UTC)[reply]
This is getting rather off-topic, but roughly speaking, the modern forms of football (association, rugby, aussie rules, American, etc.) arose from the process of codifying and formalizing the original proto-football in the mid 19th century. There was previously a lot of variation in how football was played (such matters as whether or not you were allowed to pick up the ball) and this is reflected in the range of rulesets produced. Algebraist00:22, 13 July 2008 (UTC)[reply]
In the UK it's still common to call a bicycle a push bike. The ideal tyre pressure (and energy required) will also depend on the width of your tyres. There is a very good article about this sort of stuff here.--Shantavira|feed me17:45, 12 July 2008 (UTC)[reply]
anyway... another reason for the inflation thing (true for cars as well, etc., of course) the sidewall of the tire is not a perfect spring, in fact when flexing it and returning, a lot of energy is lost as heat. as the tire turns, the sidewall is continually flexing as it reaches the contact point with the road, and unflexing as it leaves it. the higher the pressure, the less the flexing, and the less energy turns into heat. a byproduct of that is that sustained rolling around on low pressure causes the sidewalls to weaken, but that's more of a car problem than a bike problem. Gzuckier (talk) 19:40, 14 July 2008 (UTC)[reply]
ohm resistance
what is the ohm resistance of fingernail bed. if someone had bitten fingernails and touched live and neutral would electric shock scenario differ to intact skin. fossygirl —Preceding unsigned comment added by Fossygirl (talk • contribs) 13:47, 12 July 2008 (UTC)[reply]
Yes, it would be more dangerous for someone with bitten fingernails to touch a live wire, especially so if the finger was still damp from being bitten. Dry nail has a very high resistance, and dry skin can also have a resistance of several million ohms under certain conditions, but damp skin, especially if salty, can have a resistance of only several thousand ohms, resulting in a fatal current from mains voltages. Dbfirs18:12, 12 July 2008 (UTC)[reply]
Why Thailand? Seems extremely specific and not that relevant. It may help if you specific what species of cobra your referring to, e.g. Naja kaouthia, King Cobra since it likely varies. Also what sort of location? A cobra living deep in the jungle may have somewhat different behaviour to one living near an urban centre Nil Einne (talk) 19:32, 12 July 2008 (UTC)[reply]
Where does the black and white apitting cobra sleep and when does is it up and hunting? Why Thailand? Becasue it killed one of my dogs and the dogs killed one of them. —Preceding unsigned comment added by Pwjaffe (talk • contribs) 19:59, 12 July 2008 (UTC)[reply]
A few days ago I went to a show organised by the shaolin monks. Well I would like to have the scientific rundown on their performances, for some reason "I can extract chi outside of my body and obtain temporary invulnerability", doesn't satisfy me.
Bastard Soap (talk) 18:27, 12 July 2008 (UTC)[reply]
Yes, that's definitely part of it. But what about the trick were they place a spear at their throat and push with all their strength? How do you condition cartilage to withstand such a thing?Bastard Soap (talk) 19:53, 12 July 2008 (UTC)[reply]
Without having seen the trick in question, I can't be sure about this, but I would bet that -- typically for a demonstration like this -- the spear has a flexible shaft made of bamboo or some comparable material, not a completely rigid one made of some tougher substance. A flexible shaft is a lot less dangerous than a rigid one, for obvious reasons; when you push, it bends. Also, how do you know that they are pushing with all their strength? Because it looks like they do?
In any case, as it happens, the cartilage there is pretty tough stuff even without any kind of conditioning, which makes it handy for tricks like this. An episode of Penn & Teller's Bullshit! deals with this, and in fact, you can check it out on the internet. They do the trick with arrows there, but the principle is the same. They discuss it almost exactly halfway through the episode. The crappy player there unfortunately doesn't include a counter, so I can't tell you exactly where, but check it out.
I'm not putting the Shaolin guys down, mind you. They're really good at what they do; pretty awesome performers... But supernatural they ain't. -- Captain Disdain (talk) 20:24, 12 July 2008 (UTC)[reply]
One of the performances consisted of sustaining a man on 5 spears, or on just one spear. An other one consisted of extreeme twistings of their bodies. Doesn't too much stretching weaken the body?Bastard Soap (talk) 21:10, 12 July 2008 (UTC)[reply]
Sustaining a man on five spears is no big deal, really -- that's just weight distribution. If you've got a guy who weighs something like 70kg, that'd be just around 14kg of weight per spear. (A similar classic trick is to have a bunch of friends lift you using just their forefingers -- it looks crazy, but it's all about weight distribution. In the example here you can see that when the guys one one side stop lifting, the guys on the other side are suddenly in trouble.) A single spear is a better trick, but there are undoubtedly ways of doing it. I can't offer insight into it without seeing what they do, but there are many ways of doing tricks like this. (I should probably stress that it's not cheating as such; it's just that the trick isn't as difficult or insane as we think.)
As for the stretching, contortion is an old form of entertainment. It's not at all dangerous as such, though if you don't know what you're doing, I'm sure you can hurt yourself. If you do know what you're doing (i.e., have trained yourself properly, which isn't gonna happen overnight) and happen to have been born with a body that's well-suited for it, you can do pretty fantastic tricks -- it's no surprise that it's a useful skill for magicians. A cool example of this skill this can be found here. -- Captain Disdain (talk) 21:42, 12 July 2008 (UTC)[reply]
I should probably add that there's a strong tendency for people to believe that there must be some kind of a supernatural (or at least extremely complex) explanation for feats like this, because they seem so amazing. A good example can be found in thesome of the comments of another YouTube video, where people swear up and down that they are "channeling energy upwards" or focusing their energies or whatnot. In a way, it's willful stupidity in that we really convince ourselves that the weight we are lifting must be heavier than it really is. In a large part, that willingness to believe is what the illusions performed by magicians -- and, unfortunately, many cons -- are based on. (That said, many famous magicians, such as Harry Houdini, James Randi and Penn and Teller have dedicated much of their lives to educating people about these things. They don't pretend to have supernatural powers, they pretty much tell you up front that they will now show you an amazing illusion; essentially, they tell you that they're going to lie to you, and then they do so. Penn and Teller in particular have made it a trademark of theirs to show you exactly how they fool you into thinking you're seeing something magical and explaining how they do it, and then doing something even more amazing that leaves you wondering how the hell they just pulled that off.) -- Captain Disdain (talk) 21:57, 12 July 2008 (UTC)[reply]
Phases are different states of the same matter. A three-phase column could be doing mass transfer between solid, liquid and gas phases; or there could be different constituent phases, such as two different liquid phases and a gas phase.
What is the context? I know the experts on fractionation columns personally, I can find the answer if you give me a little more. (Also, a coker-fractionator might qualify as a three-phase column - heavy crude solidifies into petroleum coke while producing a liquid and gas fraction). Franamax (talk) 03:20, 13 July 2008 (UTC)[reply]
July 13
The other week someone said that the African grey parrot was probably the most intelligent dinosaur ever
Does this also mean that the African grey is also the most advanced dinosaur species that ever lived and therefore the pinnacle of the evolutionary line? —Preceding unsigned comment added by 84.70.123.255 (talk) 01:37, 13 July 2008 (UTC)[reply]
Uh, no. Intelligence does not indicate "advancement". (Humans are just as "evolved" as the housefly—evolution doesn't have an "end point" other than fitness for a given environment. We have great brains; dogs have great noses. We're all great.) And parrots are not dinosaurs, though birds are related to them. And even if there was some sort of very intelligence dinosaur, it would mean nothing about whether they were a pinnacle of an evolutionary line. --98.217.8.46 (talk) 02:09, 13 July 2008 (UTC)[reply]
Actually birds are descended from dinosaurs and many scientists do indeed consider them as "dinosaurs". From "Bird", "Most paleontologists regard birds as the only clade of dinosaurs that survived the Cretaceous–Tertiary extinction event approximately 65.5 Ma." The term "non-avian dinosaurs" is sometimes used to distinguish the traditional "reptilian" dinosaurs from birds. Axl (talk) 16:34, 13 July 2008 (UTC)[reply]
Everybody knows they are descended from dinosaurs. We're descended from little rat like creatures too but they don't call us "rats". The point is though that a bird is not a dinosaur—they're mutually exclusive categories with a little bit of overlap. --98.217.8.46 (talk) 19:47, 13 July 2008 (UTC)[reply]
No, Axl is correct. Some paleontologists do consider birds, dinosaurs. According to Phylogenetic nomenclature, reptiles are a paraphyletic group. They can be monophyletic by adding birds. So not only are they dinosaurs, birds are also technically reptiles. ScienceApe (talk) 22:42, 13 July 2008 (UTC)[reply]
In Cladistics, birds are also bacteria. I think the debate over whether birds are dinosaurs is more usefully seen as linguistic than scientific. --Allen (talk) 04:47, 14 July 2008 (UTC)[reply]
I'm currently taking a course on swiftwater rescue and although my instructor had a bit to say about utility control during massive flooding, he couldn't give me much of an answer to the following:
A city has undergone massive flooding. Rescue boats are floating down streets effecting searches and rescues. The grid is still up, as evidenced perhaps by street lights, but there are downed wires contacting the flood waters. How much of a safety radius needs to be kept from such wires?
I understand that the conductance of water increases with salinity, so perhaps sewage overflow or brackish water would make conditions more dangerous, but as a rule of thumb what ought to be a safe distance from such downed wires? Normally, the safety radius for downed wires on the ground is the full span of the length of wire (one pole to the next, the radius the wires could potentially swing) but I feel like the safety radius of wires in the water must be different. A referenced answer would be appreciated, but I'll take math guestimates to get this started. --Shaggorama (talk) 02:24, 13 July 2008 (UTC)[reply]
If the wires are in constant contact with the water, they should be pretty safe. Electricity takes the path of least resistance to ground, that will be straight through the water, people floating on top should be perfectly safe, there is no reason for the electricity to go through them. The danger would be with wires close to, be not in contact with or in intermittent, the water. A person standing ankle deep in water that touches a wire would probably to more badly hurt than one standing on dry ground - the rubber soles of your shoes will insulate you a bit normally, but if you're in water, that won't happen and you'll get the full force of the electricity through you (it's probably not a significant difference, though, it's dangerous enough without the water and you can't be worse than dead!). I think staying the same distance as you would normally (far enough away that it can't touch you) should be fine - it would have to be a very unusual situation for the electricity to pass through water to you and not just go straight to ground. --Tango (talk) 02:38, 13 July 2008 (UTC)[reply]
It would be hard to specify the required "safety radius." It is not true that "electricity takes the path of least resistance to ground." Electricity takes all paths to ground, with the current in inverse proportion to the resistance of the path. So there would ge a gradient of current intensity around a live wire, with the dimensions hard to calculate. People have shocked fish out of the water with relatively low current and voltage [3][4] (don't try this). The current should be stronger closer to the wire, but there might be enough current to stun the person in the water quite a diftance away. Also a wire at one location could liven a poorly grounded metal object, like a chainlink fence, barbed wire, a metal roof, gutters, or siding producing quite a high voltage at a remote location. Operating a boat and doing rescue in floodwaters with live wires down could be pretty hazardous. If the rescue crew had to extend a pole to poke something or hook something, it would be a good idea to have a fiberglass pole which did not conduct electricity rather than a metal one, because the voltage at two locations several feet apart could be substantially different. If the 4000 or 12000 volt primaries were live on top of the utility poles, the transformers on the poles could send 240 volt electricity to submerged meters for a long time, boiling the water without blowing a transformer fuse, even if the fuses/breakers in the building popped. Utility crews working along with the rescue crews to open poletop switches and kill the power might be a good idea. A couple of switches should suffice to kill a large area. Edison (talk) 13:37, 13 July 2008 (UTC)[reply]
The reason I asked for a "required" safe distance is because OSHA often makes safety mandates to that effect. For instance, there are required safety distances for operating in the vicinity of charged wires on the ground as well as overhead clearance for high voltage lines (I can't remember which regulation it is that makes these prescriptions). --Shaggorama (talk) 04:41, 17 July 2008 (UTC)[reply]
My potato question
Since there are already two potato questions recently, here's another:
Disclaimer: This is a question involving electricity powerful enough to kill you. Unless you know how to take appropriate safety precautions, do not try to experiment with this yourself.
Context: A really cool art installation at ThePowerPlant (if you're ever in Toronto, go to HarbourFront) consisting of cut out package fronts of everything from pantyhose to board games. Artist was Laura someone, orange light, trust me, it was cool. One package caught my eye:
The thing: A boxtop abour "The Glowing Potato" or something. This was something from the 60's that plugged into normal power and promised that you could stick a potato on it and make the potato glow.
This sounds not unreasonable to me, since the potato would have a resistance. I'm posting this here to see if anyone has ever heard of the device; and for ideas on how to actually construct one. AC or DC? Stepped-down voltage? There was no picture of the actual device on the package, but it did promise to make a glowing potato. so it's part of the North American cultural heritage :) Help is appreciated. Franamax (talk) 04:30, 13 July 2008 (UTC)[reply]
You can make an electric pickle with household voltage but that has a goodly amount of ions available because of the pickling. Most links I see about potatoes were about potato batteries. Rmhermen (talk) 04:49, 13 July 2008 (UTC)[reply]
Hmm, maybe it was a pickle. There was an awful lot to look at in those three 10-foot rooms, everything went right around the ceiling. I thought I already knew about the pickle, but they do both start with "P". I guess I'll start with a pickle, then try the higher vegetables ;) I'll try soaking a potato in salt water - in fact, maybe that's the trick, does osmosis come into play? If a potato can be a battery, then could there be some ion exchange that gets the sodium in there?
I'll have to track the art installation down again and check outside to see if the instructions are on the back of the box :) This only makes me curiouser, though I feel sure now that I do have to try that pickle. Thanx! Franamax (talk) 06:19, 13 July 2008 (UTC)[reply]
See Atom There was a recent report "Physicists Create Millimeter-sized 'Bohr Atom'". Science Daily. July 1, 2008. of mad scientists exciting an electron such that the poor thing was forced into an orbit around the nucleus creating an atom with a diameter approaching one millimeter, many orders of magnitude larger than the typical atom. No fancy orbital, just a circular orbit like a Bohr atom. The electron followed the circular orbit, like a planet around the Sun, for a few orbits. Edison (talk) 04:32, 14 July 2008 (UTC)[reply]
What I mean is, how can I get a picture of ALL the orbitals together in an atom so that I can see how they co-exist. Every picture I have seen depicts each orbital separately and singly. I want to know how they can all be together- for example, both 2Px, and 3Px are along the same axis with the same bilobed shape. Won't some regions coincide?? And they are also supposed to have different energies, but if it coincides at portions, how can that be? —Preceding unsigned comment added by 116.68.74.243 (talk) 16:10, 14 July 2008 (UTC)[reply]
This applet allows you to display any one at a time, but you can fix the axis-scaling so that (for example) you can see the different radial extent of each px. Didn't see a way to overlay them (maybe print a few out on thin paper and hold 'em up with a bright light behind, or save to a graphics-format file and overlay them in GIMP or Photoshop?). DMacks (talk) 17:02, 14 July 2008 (UTC)[reply]
High temperature changes on the human body
What are the effects of rapidly changing temperature for a person, assuming the temperatures reached are not in themselves too extreme?
Consider a person in a hot tub, going outside in the snow or any such scenario. Does it have health benefits or side effects?Bastard Soap (talk) 15:28, 13 July 2008 (UTC)[reply]
This type of a shock is likely to cause a rapid heart rate and high BP spike. Those could certainly be harmful to someone in poor health. I suppose advocates of this argue that it exercises the cardiovascular system and thus keeps it strong, but I'd think it safer to stick with more traditional forms of exercise. StuRat (talk) 17:11, 13 July 2008 (UTC)[reply]
A good example is someone with hypothermia getting put into a hot bath to try and reheat their body. Really, really bad idea, it'll burn like crazy. For the record, in that situation, the best thing to do is slow-heat the body, i.e. blankets, very luke warm water etc. — CycloneNimrodTalk?17:40, 13 July 2008 (UTC)[reply]
A better example (or at least a more common one) is the Sauna. You heat up in a room between 80 and 100 deg Celsius, then you cool down fast, with a cold water shower, dunking in a cold pool, or, indeed, rolling in the snow (careful, it hurts like hell). It is supposed to have many health benefits, including a strengthening of the immune system. As far as I'm concerned, it actually feels really good and relaxing... --Stephan Schulz (talk) 17:58, 13 July 2008 (UTC)[reply]
When it comes to snow, you can minimize discomfort by making sure that the actual surface under the snow (if the snow isn't deep) is even enough and doesn't have things like sticks and stones poking up under it. Those can smart. Another thing is to make sure that you're not rolling on pieces of ice. Typically, on a sunny day the surface of a snow bank melts when the sun shines on it, but when the sun goes down and the temperature drops, it freezes -- so you can have a lot of soft snow under a hard frozen cover. Your weight will break the cover, but that ice isn't going to do you any favors. Of course, even soft snow is going to be a bit of a shock after the sauna... but it's a pretty great feeling. Here in Finland, where this kind of stuff is our bread and butter (I just got out of the sauna about an hour ago myself) there's a general understanding that jumping right into cold water or snow after coming out of the sauna is not a good idea if you have any kind of heart trouble -- you should cool down a little before you do so. -- Captain Disdain (talk) 23:40, 13 July 2008 (UTC)[reply]
Elderly Swedes have told of getting in the sauna, then running naked out into the snow and hitting each other's naked bodies with bundles of switches (arboreal, not electrical). Sounds nuts, but they lived to a ripe old age. Edison (talk) 04:25, 14 July 2008 (UTC)[reply]
Yay Finland! I got to experience a savusauna (smoke sauna, it has no chimney) when I visited. The switches are for use inside the sauna, they take off the sweat and let you heat up even more. It was so hot my eyeballs seemed to be glazing over. Then right out and into the lake. Awesome experience, one of those "if it doesn't kill you, it will make you stronger"-type things. Franamax (talk) 21:24, 14 July 2008 (UTC)[reply]
That's just about the best kind of a sauna you can experience, so lucky you. Sauna deaths are probably not unheard of, but I'm pretty sure they're exceedingly rare... though not for lack of trying! Those guys are just nuts. -- Captain Disdain (talk) 01:27, 16 July 2008 (UTC)[reply]
Epoxy adhesives, which mix together two chemical, work well for applications where a strong space-filling adhesive is needed. Edison (talk) 04:27, 14 July 2008 (UTC)[reply]
polyethylene is pretty slippery stuff; epoxy might not be the best. i think something solventy would be better. can't say what though. i have tried to glue one of those clearish/cloudyish big plastic storage tubs (which might be polyethylene) together with cement for vinyl pipes from home depot, the kind labelled for all kinds of plastics, and it wasn't great. sure didn't penetrate, like i hoped solvent would. Gzuckier (talk) 19:30, 14 July 2008 (UTC)[reply]
Why not just use some form of plastic weld? If you can use just the right amount of heat to partially melt the plastic without puncturing the bottle, then this might be stronger than most glues. Adding more of the same material, partially-melted, will increase the strength. Unfortunately, it is not easy to get just the right amount of heat, but if you have spare bottles, you could experiment until you get it right. Some soldering guns have plastics tips for this type of "welding". Dbfirs18:49, 16 July 2008 (UTC)[reply]
I have some questions about body weight. Let's assume an average healthy adult male in America (thus, using pounds and not kilograms).
(1) Why is it exactly that when you weigh yourself several times within the same day, you will get several different readings? What exactly contributes to those differences?
(2) How wide of a discrepancy would be the "expected norm" in these different readings? I assume being "off" by 1 or 2 pounds is normal, but being "off" by 10 pounds is not. Is there some general expected norm?
(3) Is there a particular time of day when one's body weight will always be the lowest ... when would that be ... and why ... (for example, just after you wake up, just before you go to bed, right after working out, right before working out, right before eating, right after eating, etc.)? In other words, if one always wants to weigh himself at the lowest point in the day, when should that be?
(4) What is a healthy and appropriate amount of weight to lose in a given time period? That is, it is healthy to lose perhaps 1 or 2 pounds a day, but not 20 or 30 pounds a day, I assume ... is there some standard? Thanks. (Joseph A. Spadaro (talk) 18:35, 13 July 2008 (UTC))[reply]
4. You have to take in about 3,000 calories less than you need to lose a pound of weight. Since the recommended daily intake for a man is 2,500 calories, it's clearly not healthy to try and lose a pound a day. Losing a pound a week (400 calories a day) would be a serious (hard work) diet, and you should see a doctor before you try anything like it - they could say if your plan is healthy.--64.231.9.30 (talk) 22:18, 13 July 2008 (UTC)[reply]
(3) There is no answer that could possibly apply universally as each individual is, well, individual. The best strategy to monitor weight trend is to pick a particular time of day that would be least influenced by any of the usual stuff, say upon awakening and after voiding (if appropriate) naked and before breakfast. Record that weight with a 0.1 pound resolution digital scale and if your goal is to lose weight then keep the data in whatever form highly visible to yourself (and importantly, to others :-)
(4) So, WP:NOR be damned, (this isn't an article after all), two pounds per month is an appropriate challenge for either gaining or losing weight. Now, looking around at all of the information here, it should be obvious that two pounds per day (or per hour) is easily acheivable but, we're not talking about that, we're talking about "usually", so if you drop a six pack before rolling out of bed well then that's your "usual" and so go with that, consistency is the most important thing. Oh , and I think that 1 or 2 pounds a day under standard conditions would not be healthy but 1 or 2 pounds a week seems reasonable. -hydnjotalk04:14, 14 July 2008 (UTC)[reply]
I would expect your lowest body weight to be after you wake up in the morning, defacate and urinate, and weigh before eating or drinking anything. Clearly a pint of liquid refreshment weighs about a pound, and whatever you eat adds to your weight until you defacate and urinate. Any salty food should cause water retention. 2 pounds variation would not be at all surprising, just based on personal experience. Edison (talk) 04:21, 14 July 2008 (UTC)[reply]
Another factor in getting different weights could be an innacurate scale. If you are using a spring scale, for example, those tend to have readings which vary dramatically based on humidity, since they can "stick" if used in the bathroom after a shower. StuRat (talk) 04:27, 14 July 2008 (UTC)[reply]
An anonymous (well, mostly) poll and invitation:
Step right up and "weigh-in" RDers, c'mon now, this is one of the least serious polls in which to participate!
If you are trying to gain weight then increment: ..................................... #0
If you are trying to maintain weight then increment: .............................. #1
If you are trying to lose weight then increment: ..................................... #4
If you are not trying to consciously control your weight then increment: ... #1
If you are not understanding WTF is going on then don't dare touch this: .. #43
Results (update #5): The folks not knowing WTF is going on seem to know it all!
(Original research warning...) I've been taking data on this very question and I find that my weight varies over a range of about two to three pounds each day. And this stands to reason: Drink a 16 ounce glass of water and you've just "gained a pound". Eat a meal and you've "gained" another pound. Later, use the toilet and you lose most of that "gain". Go for a long walk, run, or bicycle ride, sweat out 16 ounces of sweat, and you've also "lost" a pound.
In other words, small changes don't matter. This variation can, to some degree, be mitigated by weighing yourself at the same time of day each time you weigh yourself, perhaps in the morning after you've voided your bladder and defecated. But even then, only pay attention to the long term trends (unless you're like me and are doing it just to collect interesting data for later use in an encyclopedia).
My point regarding the use of a high resolution scale was to at least eliminate that variable. So, we all seem to agree that the best strategy to monitor a weight trend is to do what we all said (AM, after voiding (if appropriate), and before eating or drinking anything (unless it is a standard amount each time-in my own case it happens to be 8 ounces of a medicine). Now, given all of our collective wisdom, we seem to acknowledge that there is day-to-day noise in the data however, over several weeks of daily data, a trend can be inferred. I've been taking this data on myself for well over 20 years and am confident of its usefulness. -hydnjotalk15:30, 14 July 2008 (UTC)[reply]
Note that the surface on which the scale rests also has an effect on the reading. My spring scale gives my weight as 130 lb on a ceramic floor and 136 lb on a carpeted floor, for example. --Bowlhover (talk) 07:58, 15 July 2008 (UTC)[reply]
if someone were to have a faint leak, so that they could smell the gas, and as a result decided to air it out, but continued to smell it faintly, would inhaling it -- I AM NOT ASKING FOR LEGAL OR MEDICAL ADVICE -- be harmful? Ought they to leave the room? —Preceding unsigned comment added by 82.120.227.196 (talk) 19:10, 13 July 2008 (UTC)[reply]
The biggest danger of a gas leak is not inhaling it but that it is VERY flammable. You ought to call the gas company (or maybe even the fire department) and get it fixed NOW. See Natural_gas#Safety. --98.217.8.46 (talk) 19:40, 13 July 2008 (UTC)[reply]
Continue airing it out, get out of the house, call your local emergency gas leak number. If you're in the UK, this is a good guide. Call 0800 111 999 from outside your house, which should have the windows open, the gas switched off, etc. If you're elsewhere, I'm sure there are local guides and numbers. 79.66.54.186 (talk) 19:42, 13 July 2008 (UTC)[reply]
The negative effect is that your house might explode!. Leave the house, use your neighbor's phone to call the gas company. APL (talk) 20:00, 13 July 2008 (UTC)[reply]
Obviously, I second what everyone else says about the danger of explosion, and you do need to get out of the house. However, to answer the specific question asked, natural gas is not toxic (according to Natural gas, anyway), the only danger from inhaling it is that you may not be inhaling enough oxygen and could asphyxiate. However, if there's enough gas in the room for you to be concerned about being poisoned, there is enough to warrant getting out of there, so it's purely academic. --Tango (talk) 21:15, 13 July 2008 (UTC)[reply]
Also, for the record, if the odor is really really faint, then the amount of gas present is probably tiny. Natural gas is odorless, so compounds are added after the product is refined to assist in detection of leaks. These compunds, often thiols (AKA mercaptans) are so pungeant that we detect them in units of parts per BILLION! For instance, let's say the gas you were cooking with was propane odorized with ethanethiol: the LEL for proapane is 2.1 * 10^7 ppb, but you can detect the odorant at quantities as low as 2.8 ppb. If we call > 10% of LEL our danger zone, you could detect the gas by smell and still have a safety factor of 1 million! Neat huh? Yay technology!
Obviously, you should still play it safe and call the utilities or fire department. Depending on where you live, if you are positive the leak is small, it may actually better to minimize ventilation (close windows) before leaving the house if you know help will arrive soon. Natural gas is heavier than air and will collect in pools which helps detection if electronic gas detectors are used: if the house gets ventilated, the explosive hazard is minimized but it becomes much more difficult to pinpoint the source of the leak. Again, this is ONLY if you know help will arrive soon, you know what detection capabilities they have and you think the leak is small. You don't want to fill up your house with gas. --Shaggorama (talk) 22:03, 13 July 2008 (UTC)[reply]
I think there's an error in your calculation - we can smell the odorant at 2.8 ppb *of the odorant*, but the odorant isn't 100% of the gas, obviously, so you need a higher concentration of the gas in order for the odorant to be high enough. I'm not sure what proportion of the gas is generally odorant, but it's quite small, so the safety factor is nowhere near a million. And I would advise against trying to keep the gas in to aid detection - let the experts worry about finding the leak once they get there, don't take any risks. --Tango (talk) 23:03, 13 July 2008 (UTC)[reply]
If the natural gas is at a high enough percentage of the air in the structure to explode, clearly the explosion, fire, and structure collapse could have devastating effects. But humans expel methane under the covers while they sleep, and I have never heard of anyone dieing from exposure to small amounts of it. If you report a possible gas leak to the gas company and/or the fire company, they should be able to test for the presence of it. Methane is actually odorless; an odorant (butyl? mercaptan) is added to make it detectable. Edison (talk) 04:12, 14 July 2008 (UTC)[reply]
I tried calculating the concentration of propane indicated by the lowest perceivable concentration of its odorant, ethyl mercaptan. Estimates of ethyl mercaptan's odour threshold range from 0.01 ppb to Wikipedia' figure of 2.8 ppb, so I abandoned this approach.
This paper indicates that around 40% of elders cannot detect the odorant at a level associated with a concentration of propane at the Department of Transportation`s safety limit, which is a fifth of propane`s LEL. Three of the 110 subjects could not even smell the ethyl mercaptan when it was at a concentration that would indicate a risk of explosion. So even if the odorant is barely perceivable, the risk of not taking further steps to remove propane is very small, but not negligible. --Bowlhover (talk) 09:10, 14 July 2008 (UTC)[reply]
So is the answer above wrong which talks about ethyl mercaptan, or are they used together, or do different gas companies use different odorants? Or is it propane versus natural gas? I would assume they have different detectability levels, which would also affect the analyses. Edison (talk) 17:39, 15 July 2008 (UTC)[reply]
I think it's at the discretion of the manufacturer what chemical they use as odorant, so long as the added odor meets certain government standards for threshold detectability of the gas. Go to a local camping supplies store and buy the cheapest small bottle of propane there and compre its odor to the most expensive brand: strong probability the cheapo smells worse. --Shaggorama (talk) 12:20, 16 July 2008 (UTC)[reply]
I don't think so, no. To be O, you need to get the O allele from both parents. Someone that is AB has an A allele and a B allele, so they can't have an O allele to give. There is a table on ABO#Inheritance which shows the possible inheritances. The + part is fine, though, you only need one parent to be Rhesus positive for you to be. Of course, there is always the possibility of random mutations and what have you messing everything up, so the blood groups not matching isn't 100% proof that they aren't your biological parents, but it is unlikely. Note, AB- is a very rare blood type (1% or less of the population, depending on where you are - see Blood type for a table), so you may want to double check you've got that right. --Tango (talk) 20:21, 13 July 2008 (UTC)[reply]
See also hh antigen system -- there is a tiny chance that both mother and father could have the recessive h gene, and the child could come up hh (the Bombay phenotype) which means he would have O blood regardless of the rest of his genotype. --Trovatore (talk) 20:37, 13 July 2008 (UTC)[reply]
I've also just read in the ABO article that AB expresses less strongly than A or B individually, which I think means AB people are sometimes detected as O. That suggests that it's possible that, in fact, both parents and the child are AB, although that also would be very unlikely. --Tango (talk) 20:43, 13 July 2008 (UTC)[reply]
The answer is yes, for a wide range of reasons. If you're concerned about the identity of your biological mother and father, I suggest you speak to your parents and to your doctor. Any answer we provide here is apt to be imcomplete or misleading. TenOfAllTrades(talk) 01:13, 14 July 2008 (UTC)[reply]
There was a woman who was told that her true biological child could not be her actual child. It turned out that she was a Chimera with her ovaries possessing different DNA than her blood would imply. There are also cases of hospitals accidentally switching blood samples and reporting erroneous results. Just saying. Edison (talk) 04:07, 14 July 2008 (UTC)[reply]
We used to test our blood types in high school biology, but they stopped doing it when students were going home with difficult questions... PlasticupT/C12:57, 14 July 2008 (UTC)[reply]
I've heard that claim before but I suspect it may have more to do with fear of infectious diseases rather then children finding out their parents may not be who they thought they were (although I'm sure it was somewhat of a problem). Nil Einne (talk) 18:35, 14 July 2008 (UTC)[reply]
I find it quite believable. One of the major concerns in any medical study involving large-scale blood typing or DNA testing is dealing with the fact that about 20% of the subjects cannot possibly be the children of their supposed fathers. --Carnildo (talk) 22:05, 15 July 2008 (UTC)[reply]
Conductive napalm? Railgun + conductive flammable liquid = long range flamethrower?
Wouldn't firing a flaming liquid at very long range with a large ratio of total volume to surface area effectively cause it to cool down too rapidly to be of any use? --98.217.8.46 (talk) 03:10, 14 July 2008 (UTC)[reply]
Right, but it's usually not going very far or at very high speeds, and it's not usually kept in a long thin stream. If you change the characteristics around it'll radiate heat differently than how it does when used in bombs or flame throwers. --98.217.8.46 (talk) 20:47, 14 July 2008 (UTC)[reply]
Liquid Sodium etc are flammable/conductive - unfortunately liquids tend to spread out as they travel because they have no integrity - maybe this would be a problem.87.102.86.73 (talk) 10:50, 14 July 2008 (UTC)[reply]
Liquid sodium, interesting. Maybe some kinds of gasoline/sodium mixtures might help make it conductive. Yea, in order to make a good flamethrower the liquid has to be a thick gel, this would keep it cohesive. Napalm is actually a thickening agent. ScienceApe (talk) 18:57, 14 July 2008 (UTC)[reply]
This page: [5] document that using this idea to propel ships has been considered several times. Basically, the underside of the ship follow the same schematics as a railgun, moving conductive seawater. More info may be found in the Magnetohydrodynamics article. So basically, it's possible in principle. The use of a plasma instead of a liquid may be more interesting though, as there's ways to keep that together. EverGreg (talk) 21:26, 20 July 2008 (UTC)[reply]
Ultraviolet light
So if you go to Ultraviolet, you'll see it only explains how humans deal with ultraviolet light. The only other animal this could possibly apply to is non-feral pigs as they tend to be hairless.
So one wonders, what about other creatures. Are reptile scales any good protection against UV light? It would seem likely they are. What of bird feathers, animal hair, fish scales, dolphin/whale/seal skin, insects and other anthropods, etc.? The Talk:Ultraviolet looks abandoned. Well, is this information somewhere else on Wikipedia that someone knows of? William Ortiz (talk) 23:03, 13 July 2008 (UTC)[reply]
Certainly. Scales, feathers, and hair are all good protection from UV light. Additionally, just wearing clothes will protect you from UV light as long as it is fairly opaque. Whales and other marine animals live in the water where the water itself protects them from UV light. You might also wonder about pigs and hippos. They have melanin in their skin (just like us), and also use mud to help protect them. ScienceApe (talk) 23:45, 13 July 2008 (UTC)[reply]
Eumelanin, much more so than phaeomelanin, is the principle mechanism of UV protection in skin. Many, many animals have eumelanin in their melanocytes or melanophores in skin and scales. Moreover, hair, feathers and exoskeletons contain much melanin also. The role of melanin in UV protection is highly conserved throughout the animal kingdom. Rockpocket02:59, 14 July 2008 (UTC)[reply]
The bridge of the nose and light coloured noses are too of both cats and dogs. Tattooing is sometimes used to try and prevent this although I don't think it's that effective [6]Nil Einne (talk) 18:27, 14 July 2008 (UTC)[reply]
Why is it that light colors which reflect heat make people vulerable to sunburn while dark colors which absorb heat protect from sunburn? William Ortiz (talk) 22:38, 14 July 2008 (UTC)[reply]
It isn't exactly "heat" that causes sunburn. Dark eumelanin absorbs UV, which means there is less of it around to damage the unprotected cells underneath. Light coloured phaeomelanin can't absorb UV as well, so more of it damages the skin cells underneath, which results in sunburn. Interestingly enough, darkly pigmented skin appears to reflect UVB and UVC better than lightly pigmented skin. It appears that scattering by melanosomes with high relative refractive indices plays a major role in this. Rockpocket01:20, 15 July 2008 (UTC)[reply]
I can't lay my hands on the ref but I have read that the mechanism of melanin protection is that the cell accumulates it and tows an umbrella of melanin into place to shield the cell nucleus as a specific response to UV radiation. I'll try to chase that down if anyone wants, 'tho I'm not exactly sure where to look anymore. Also, pigs definitely do get sunburn if you leave them out in the sun, Yorkshire pigs anyway (pink-white skin + I can't believe we don't have an article on Yorksies!). Franamax (talk) 07:20, 15 July 2008 (UTC)[reply]
Right, it isn't heat that causes sunburn. It's UV light. You can wear a thick winter coat on a hot summer day, and you won't be sunburned because the coat will block UV light. You'll pass out from heat stroke though. ScienceApe (talk) 17:14, 15 July 2008 (UTC)[reply]
That's right. It's not the reflection of heat that is important here, it is the relection of light. Specifically, lighter coloured clothes would reflect light (of all wavelengths including UV) onto the wearers face making them more vulnerable to sunburn. Jdrewitt (talk) 19:54, 16 July 2008 (UTC)[reply]
July 14
colostrum
Cow's colostrum are rich in lg M.If we consume products with these cow colostrum, can it really increase the immune system and boost our health.?218.208.43.111 (talk) 02:00, 14 July 2008 (UTC)Rainy[reply]
First, it is IgM, not lg M. It is a basic antibody found in B cells. Ingesting IgM does not magically get it into your blood stream and into your B cells to boost your immune system. Next, you will probably ask about shooting it straight into your blood stream. If you did that, your body will recognize it as a foreign invader and kill it off before any hoped for beneficial effect could take place. -- kainaw™02:25, 14 July 2008 (UTC)[reply]
IgM will be absorbed across the intestine of a nursing calf and could possibly be absorbed by a human also. The problem there is that the IgM antibody will most likely only signal the immune cells found in cows. Antibodies work in a two-stage process, they recognize an antigen but they also have to activate a leukocyte to initiate a comprehensive immune response. I doubt that cattle IgM has evolved to activate human immune cells, so the IgM antibody itself might neutralize a single pathogen, but it would not convey the lasting immune benefit that calves experience. Franamax (talk) 02:46, 14 July 2008 (UTC)[reply]
Animal Ig can be used to boost immune response (Antivenin) but I don't think that cow's milk Ig is a good immune booster as said by the posters above. However, I think milk can indirectly improve the immune system though as it provides the amino acids that can be used to manufacture Ig's.--Lenticel(talk)03:06, 14 July 2008 (UTC)[reply]
As I noted, ingesting of antibodies is not an effective method of use (which I assume the questioner means by "consume"). Antivenin is delivered intravenously (or within range of plenty of capillaries if there is a major rush). -- kainaw™12:08, 14 July 2008 (UTC)[reply]
Kainaw, the flaw in your reasoning is that for calves, ingestion clearly is an effective method of use, evidenced by the fact that major purpose of colostrum is to boost the immune system of the calf, and calves drink milk rather than shooting up. Clearly, the antibodies are capable of passing the intestinal barrier (caveat - it's possible the immune stimulation is generated within the gut, then passed to the body system by some other method). The question here seems to be whether the IgM antibodies in colostrum have an immune-stimulative effect in the human body, regardless of the method of delivery. Franamax (talk) 12:31, 14 July 2008 (UTC)[reply]
The article on breast and formula milk I was reading in New Scientist the other day certainly seemed to suggest that most of the immune system stuff in milk works only on the gut population. Very little of that stuff passes into the blood stream. This is based on my reading of it though, not on having any sort of relevant qualification. 79.66.54.186 (talk) 17:34, 14 July 2008 (UTC)[reply]
The questioner asked about humans, not calves. In humans, antibodies from other animals are not effectively passed through to the blood stream through ingestion. As the anon pointed out, they aren't even passed effectively from human to human through ingestion - but human to human is a lot more effective than cow to human. -- kainaw™19:13, 14 July 2008 (UTC)[reply]
Well, I did put that caveat in there. Turns out there's a little more to the story too. A newborn calf is able to directly absorb the antibodies [7] for 24 hours and I found some indications the same is true of human babies. After that, the effects would indeed be confined to the gut itself. Given that, I would go back to saying that the cow antibodies would be able to bind and neutralize antigen but would be unlikely to stimulate the immune system. For any 12-hour-old humans reading this though - yes, colostrum is good for you! Franamax (talk) 19:52, 14 July 2008 (UTC)[reply]
Bond Energy & EN
How is bond energy affected by the electronegativity difference between the 2 atoms? Here it says the more polar the bond, the stronger it is. But why is this so?
125.238.241.210 (talk) 07:30, 14 July 2008 (UTC)[reply]
So, my crackpot question is whether it is feasible to use gyroscopic precession as a method of propulsion. My main idea involves three wheels: one large one and two smaller ones, fixed rigidly to the first. Imagine two saucers fixed side by side to a large dinner plate, such that the outer edge of the saucers were lined up to the outer edge of the plate, and the inner edge of the saucers were lined up with the center of the plate:
(00) <- More or less like this, never mind the crudeness of the diagram. The point of this alignment is that if you rotate both the saucers and the plate counter clockwise (for example), and then observe one particular spot on the edge of one of the saucers, the net momentum of that spot will change depending on its position with respect to the outer edge of the plate.
Assume each object is rotated such that, measured separately, the outer edge would maintain a (completely arbitrarily selected) speed of "1". At the point where the outer edge of the saucer is lined up with the outer edge of the plate, the *net* speed should be very nearly "2" - as the rotation of the plate will be added to the rotation of the saucer. But as that point rotates around to the place closest to the center of the plate, it will now be travelling against the rotation of the plate - for a net speed slowing to very nearly zero.
And now, to do something useful, perhaps: Instead of having our plates and saucers all aligned on the same plane of rotation, we tilt the saucers up at a 45 degree angle. From the side, it might look something like this:
_\_/_ <- assuming we were trapped in a horrible ASCII world it might, anyway. The point in doing this, is that the edges closest and farthest from the center of the plate will still be travelling parallel to the rotation of the plate. My "outermost" saucer edge (now also "uppermost") - will still be travelling at a speed of approximately "2", and my "innermost" edge (now also "lowermost") - will be travelling at a speed of approximately "0".
The other predicted effect is that the saucers, by virtue of being constantly forced by the plate's rotation out of their own planes of rotation, will exert a constant and linear force via gyroscopic precession. Being as how momentum has now been maximized at the outer edge, and minimized at the inner edge - this force should be asymmetric in nature, providing a unidirectional "push" as it were rather than simple torque. The "down" phase will exhibit very little precession effect, due to possessing very little angular momentum, leaving only (mostly) the precession effects of the "up" phase significantly affecting the whole system.
I will be the first to admit if I have overlooked some profound and perhaps hilariously obvious fact which invalidates my scheme. But I would be most greatful if someone could point it out to me, so that we may both share the laugh! :)
Nothing's conclusive, it's just a question of what is most likely based on the evidence we have. In most cases, inconstancy in various physical laws (say, the strength of gravity) would have real implications for how we observe the world today. --98.217.8.46 (talk) 14:19, 14 July 2008 (UTC)[reply]
Conclusive just means "sufficient to draw a conclusion". Plenty of scientific evidence is conclusive. None is 100% certain, though. --Tango (talk) 17:26, 14 July 2008 (UTC)[reply]
Well, I was assuming he meant "sufficient to draw a totally certain conclusion". Which just doesn't happen in science or anything else where you are talking about rigorous methodology. --98.217.8.46 (talk) 17:36, 14 July 2008 (UTC)[reply]
hi...i just want ti know which part of the has seven (7) bones while you are still a baby and becoming three (3) as you grow up? I really appreciate the help. —Preceding unsigned comment added by 212.43.3.2 (talk) 17:51, 14 July 2008 (UTC)[reply]
I presume you mean which part of the human body. If you think about it the answer will pop into your head. That is a very strong hint by the way. Jdrewitt (talk) 18:17, 14 July 2008 (UTC)[reply]
Putting the ethics aside and as a tought experiment, imagine someone traveling through the future stopping every 20 years to impragnate his own daughter. Would the end result (after, say, 100 generations) be someone with an almost identical genome or do other factors come into play. How much do random mutations mess it up? What kind of genetic traits would it push forward? What would be the genetic dangers there? 190.190.224.115 (talk) 20:27, 14 July 2008 (UTC)[reply]
(light-hearted aside: Oh, we so badly need a template to handle questions like this, warning that the reference desk does not give advice on time-travel related incest or ancestoricide, complete with stern paradox warning sign icon. :) -- Finlay McWalter | Talk20:36, 14 July 2008 (UTC)[reply]
Time travel for the purpose of incest is forbidden! Your question has been removed three days before you posted it.
Genetic dangers would be those associated with severe inbreeding. It's not genetically any different than a person reproducing and then impregnating their daughter and then the granddaughter. If someone was really dedicated to the idea and got started early enough they could easily impregnate their great-granddaughter too, or even more, if they started around age 13 and reproduced every time the "daughter" was 13. Yuck. It wouldn't end up with an identical genome, you'd just see the side effects of lots and lots of recessive genes. As for what genes it would encourage; no way to know that ahead of time. Historically inbreeding has encourage a wide variety of deleterious genes in humans. --98.217.8.46 (talk) 20:41, 14 July 2008 (UTC)[reply]
I agree you wouldn't end up with an identical genome, since each daughter would get a different combination of the father's genes, but I think you would get an ever greater proportion of alleles coming from the father, since the only other source of genetic information (the man's original mate) would be further and further back in the family tree, thus contributing ever less of the genome, and the rest has to come from the father's genome. To reach 99% coming from the father, you would need 7 generations of daughters. By that point, almost any gene for which the father was homozygous, the daughter would be identical. For heterozygous genes, the daughter could be identical or could be homozygous with two copies of either of the alleles present in the father. I'm not sure what the odds of each option is, but I suspect it's uniform, so 50% chance of being identical and 25% of each of the homozygous cases. --Tango (talk) 22:59, 14 July 2008 (UTC)[reply]
I don't think you could expect to achieve more than a 75% match on average. That's because the father and mother each contribute 50% of the genes, but there's nothing to force the combination to exactly complement each other.Say the father has gene pairs aA, bB, cC, and dD. Even if the mother has identical genes, the offspring would not likely have all the necessary genes to be your "clone". Using the aA pair as an example crossed with another aA pair, the offspring might end up with aa, aA, Aa, or AA. Only half have 100% of the necessary genes, while the other half have only 50% of the genes needed to match the father. Back to four gene pairs: while there is a 1/16 small chance of having 100% gene coverage (such as aA, Bb, cC, dD), there is a 1/4 change of having 87.5% coverage, 3/8 chance of 75% coverage, 1/4 chance of 62.5% coverage, and 1/16 chance of only 50% coverage (such as aa, bb, CC, dd). With more genes, the change of 100% coverage continues to decrease, but the average coverage remains 75%. (I've ignored xy genes for now for simplicity.) -- Tcncv (talk) 01:48, 15 July 2008 (UTC)[reply]
For an exact match, you may well be right. As I said, all you can say is that after several generations most of the genes will come from the father, but not necessarily in the same combinations. For example, consider the father is ab and the mother is cd for a given gene. The options for the first daughter are {ac,ad,bc,bd} with equal chances. Then, for the second daughter, in each of those cases, you get {{aa,ac,ba,bc},{aa,ad,ba,bd},{ab,ac,bb,bc},{ab,ad,bb,bd}}, all having equal chances again. That gives a 50% that both alleles will come from the father. If you do another generation, you'll get an even higher chance of both alleles being from the father (75%, I think). --Tango (talk) 02:15, 15 July 2008 (UTC)[reply]
If that logic is extended to 100 generations, the chances for any of the pairs {aa,ab,ba,bb} in the daughter would approach 25% each, while the chances of the remaining combinations {ac,ad,bc,bd} would be negligible. Taking ab as equivalent to ba, we would have a 50% chance of "cloning" the gene pair of the father. Taking aa and bb as each a 50% match to ab, we have a 50% chance of a 50% match. Together that gives us an average match of 75%. Given a large number of genes, the great majority of 100the generation offspring would hover be 65% to 85% match range.
Interestingly, it doesn't matter whether the 99th mother had gene pairs aa, ab, ba, or bb. The average match for the daughter to the father would be 75%. (Left as an exercise.) Note that all this only considers gene pairs with two distinct halves. It doesn't count genes that start out like aa in the father. -- Tcncv (talk) 05:01, 15 July 2008 (UTC)[reply]
Note that time travel into the future is not only permissible, it is inevitable. We all travel into the future by one year per year. You can get the same genetic effect by simply freezing enough sperm and then using some for each generation. To avoid the ethical problem and speed up the process, I recommend that you use mice instead of men. -Arch dude (talk) 00:25, 15 July 2008 (UTC)[reply]
"How much do random mutations mess it up?" Mutations are much more likely to prove fatal than beneficial, so such mutations would likely be quickly eliminated. Even if a daughter with such a mutation is impregnated, as long as the likelihood of surviving and giving birth is lower with the new gene than without, the next daughter would likely not have the mutation.
100 generations seem much too short of a time for beneficial mutations to appear. If one does appear, it would disappear as soon as the father reproduces with a daughter who does not have the mutation. --Bowlhover (talk) 07:45, 15 July 2008 (UTC)[reply]
I'm assuming 190.190.224.115 intended for the father and daughter to breed as many times as necessary to ensure a succeeding generation will exist. --Bowlhover (talk) 15:54, 15 July 2008 (UTC)[reply]
I don't know, but would caution against mixing your own chemicals, since some combos, like chlorine bleach and ammonia, can produce toxic gases. I'd just use diluted ammonia for window cleaner, since it works well without the alcohol. StuRat (talk) 02:30, 15 July 2008 (UTC)[reply]
s it true that due to Earth's rotation, water and air masses turn in different directions in both hemispheres. For example, if I am draining water from a sink in Sydney, would the water really rotate clockwise but in Los Angeles, it would rotate counterclockwise? What is the source of this phenomena? Do we have an article on this? Can someone perhaps shed some light on this?--A Real Kaiser...NOT! (talk) 06:27, 15 July 2008 (UTC)[reply]
This has always interested me, since childhood (and unlike the poster in a thread above, no we don't all time travel into the future one year per year, I've remained stuck in little kid mode!) when I would sit in the bathtub and twirl the draining water backwards - it would always go back into clockwise rotation, basically obeying the right-hand rule. Is it at least generally true that everything drain-wise we commonly see in every day life spins clockwise? Does anyone have a counter-example? Southern hemisphere 'pedians are welcome to post, but please type backwards.
I've always been curious about the no-Coriolis explanation - why do businesses design right-hand bathtubs? These are the questions that plague me :) Franamax (talk) 06:50, 15 July 2008 (UTC)[reply]
Well I just filled my sink and let it go...it made a nice counterclockwise cyclone even though I'm in the northern hemisphere :-p Someguy1221 (talk) 07:25, 15 July 2008 (UTC)[reply]
In the northern hemisphere, the Coriolis effect applies a small tendency to rotate draining water counterclockwise. This is the reason low-pressure weather systems rotate in that direction north of 0 degrees. --Bowlhover (talk) 07:39, 15 July 2008 (UTC)[reply]
Hmm. I get kitchen sink = clockwise, bathroom sink - didn't work 'cause of the plug thingy, bathtub = clockwise (after I found the plug, I only take showers). My family and friends are going to think I'm a bit weird when I visit them over the next few weeks and puddle around their houses :) I do recognize the paradox vs. the Coriolis effect and I'll stop when I find a ccw drain, honest. Otherwise, Someguy will have to mail me their sink. Ahh the unsolved mysteries of childhood - thanks all for the input! Franamax (talk) 21:50, 15 July 2008 (UTC)[reply]
I don't know about bathtubs, but I've certainly seen water in drains rotate in both directions, as well as water in toilets. The direction of water in any specific toilet, though, is constant because the water used to flush it is injected in the same way every time.
In a system as complicated as the human body it is difficult to say without more details. (Standard Wikipedia Disclaimer: The reference desk does not offer medical advice.) The interdependencies and what ties into what within a living organism, particularly a set as complicated as mammals. If you're really concerned about it, my first guesses would be a drug interaction, possibly between any anesthesia you were given and any other medication you were taking, or depending on how invasive the procedure it is possible there was nerve damage. You also mention infections, and given the proximity of your mouth to your central nervous system I suppose it might be possible the infection traveled. Take the above with a grain of salt, as I'm not an expert, but my short answer to your question would be, "Yes, anything is possible. If you've had any kind of weird changes in your medical condition after a procedure, see a doctor." EagleFalconn (talk) 13:06, 15 July 2008 (UTC)[reply]
I'm confident that the answer is "No" directly, but "Yes, possibly" indirectly. Dental surgery could, like any other surgical procedure, allow infections to take place which may then cause loss of sight. As EagleFalconn also said, there is also the possibility of drug interaction or nerve damage. I'm going to take a guess that you are concerned about either your or someone else's loss of vision since this is the second post you have made regarding loss of vision. I really suggest you ask a physician if you are concerned because honestly, they won't bite. — CycloneNimrodTalk?20:36, 15 July 2008 (UTC)[reply]
I can't see how it looks like a stink bug (or shield bug in UK) The mystery beetle had a separated head and it is about twice as long as it is wide. The stink bug has the head joined directly to the thorax and is about about as long as it is wide. I find it hard to disagree with your initial phrase EF. Richard Avery (talk) 13:52, 15 July 2008 (UTC)[reply]
To be honest I agree with you, I'd always wondered why they were called stink bugs. I'd never experienced any particularly putrid odors. My guess is that its a regional misnomer, but the snide remark wasn't really necessary. EagleFalconn (talk) 14:27, 15 July 2008 (UTC)[reply]
The BBC link mentions that it looks similar to arocatus roeselii. In my opinion they look so similar that I would bank on it being one of them. Wikimedia Commons has an image which is labelled as arocatus roeselii. See below. Very close likeness of the markings. Arocatus roeseliiRichard B (talk) 14:35, 15 July 2008 (UTC)[reply]
Just so we're clear where the confusion lies (come on, does anyone here really think they can out-classify the London museum of natural history? Especially given that we're just working off of a single image from an article, and they have live samples), from cnn.com:
“
The bug resembles the Arocatus roeselii, which is usually found in central Europe but is a brighter red and lives on alder trees.
Entomologists suspect that the new bug could be a version of the roeselii that has adapted to live on plane trees but acknowledged that it could be an entirely new species.
According to this Snopes article, sugar is insoluble in gasoline and cannot even reach the engine. Instead, it's blocked out by two filters specifically designed to keep contaminants out of the engine. --Bowlhover (talk) 08:42, 15 July 2008 (UTC)[reply]
The Straight Dope also discussed this as an SD Staff Report, and indicated that it would, in fact, be bad for the engine. When objections surfaced along the lines of the Snopes article, they tackled the question again and came to the same conclusion, this time after conducting an experiment. (It apparently didn't ruin the engine, but certainly put it out of commission for the time being.) -- Captain Disdain (talk) 11:54, 15 July 2008 (UTC)[reply]
A note of clarification. Both the Snopes article and the Straight Dope article suggest that while a large quantity of sugar in the gas tank could immobilize an automobile, it has nothing to do with any direct effect on, or harm to, the engine. Rather, the accumulation of gasoline-insoluble sugar is apt to clog up the 'sock' or the fuel filter, starving the engine for gasoline. TenOfAllTrades(talk) 14:02, 15 July 2008 (UTC)[reply]
For a more general answer - everything2 is not considered a reliable source by wikipedia's policies, and it is a site that anyone can sign up and add content to, so you probably could not use this as a source e.g. if you were to write a paper. It may be worth your time to check out the sources that it lists at the bottom though. --Random832 (contribs) 18:24, 18 July 2008 (UTC)[reply]
Can one person create the sound of a barber-shop quartet?
I watched a cartoon recently where one of the characters sings a song in the style of a barber-shop quartet i.e. 4 harmonised tunes all sung together.
This got me wondering. Is there any physical reason why a single person couldn't produce the sound of many notes (e.g. a chord or a harmonised tune) using only one voice? Presumably, if a single speaker connected to an amplifier can play music comprising many different notes and instruments at one time, a human's vocal chords can do the same? Could someone train their voice to do this?
Beyond the specific and limited capabilities of throat singing, though, I'd say the answer is No. A typical speaker can produce arbitrarily complex waveforms, because it's constantly driven by a magnet, which pushes air in whatever pattern is encoded in the signal. The voice, though, is closer to a musical instrument, with a single vibrating surface to generate the sound, driven by resonance when wind is passed over it. You're not singing by actively vibrating your vocal chords; you're pushing air over them, which makes them vibrate. You can vary your throat shape to accentuate harmonics, but I would think you can't make completely independent sounds. jeffjon (talk) 15:06, 15 July 2008 (UTC)[reply]
More precisely, tenor, lead, baritone, and bass. Lead is roughly a second tenor, but is not called a tenor. It's not impossible that one person with a large range could sing all of these -- actually a lot of barbershop tenors are natural basses, because barbershop tenor is normally sung falsetto.
Barbershop baritone is one of the most thankless roles you can imagine -- it's extremely difficult, because you're typically on the third or the seventh, but no one hears you because you're in the middle of the chord and don't have the melody. I'm a natural baritone, but sang lead because I don't have a good enough ear for barbershop baritone. --Trovatore (talk) 07:23, 16 July 2008 (UTC)[reply]
i note that the graph on that page is oxygen/time (essentially calories per time) vs velocity. since the OP asked about calories per distance, that turns out to be the slope of the graph. now, the slope of the graph for walking up to the point where running starts and the slope of the running graph after that is about the same, indicating that in fact the calories used per distance is about the same whether running or walking, if you don't try to walk at an unusually rapid speed when you would more naturally be running. this agrees with what i've heard elsewhere, which is that calories per distance for a human is essentially constant with velocity except at very high velocities, and also at very low velocities, but that's just because the 2000 calories a day you need for your basic metabolism becomes significant. this also makes sense evolutionarily, where efficiency would be something that would be selected for, except at war emergency power life or death speeds. but of course, arguments from evolution can be used to support either side of an argument if you're clever. Gzuckier (talk) 19:47, 16 July 2008 (UTC)[reply]
about "some naive hypothesis at odds with basis of physik "
1--Can i have page history from july o9 08 till july 15 08 ?
2--It was my mistake that part of my writing above subject is not edited ? I am new user. I wrote three hypothesis: I- About a hypothetic particle that supposed to be the only basis component of common particles. II- About some " corrections" in the formula of Lorents-Ajnstain. III- About the gravity charge as +,- f^0.5 (That is +,- G^0.5 ). This charge together with electric charge supposed to be the only forces in equilibrium in ten kind simple common particles. They (Hypothesis)are naive because are not supported by sophisticated math. It used an simple math because the writer is illiterate on high math, so in physic.
But they are controversial with basis of contemporary physic, linked together to prove that no-thing can be created by nothing,that the supposed unique particle can not be created can not be destroyed, that the annihilation of matter is a wrong concept and the photons are common particles ( structured by the same unique particles.) which for outer frame are both electric and gravity null charged .
The user hoped that any bright lad or lads will find interesting the meaning of the hypothesis to search further and fill the lots of gaps. 70.248.135.115 (talk) 17:56, 15 July 2008 (UTC)[reply]
Just click "history" at the top of the page on any page in Wikipedia to get the history of edits to the page. Click on a version number and you'll see the page exactly as it was on that version.
Wikipedia is not a place to post your original work and ask others to critique it. It is a collection of references from published, respectable resources. You appear to be in need of a message board specializing in physics - and one specializing in basic English grammar. -- kainaw™18:02, 15 July 2008 (UTC)[reply]
Why don't leaves form a thin layer like a bag over a tree?
I was struck going under some trees by how many branches they had with leaves all higgley piggledy up the trunk with one lot of leaves covering another and gaps all over the place. I would have thought the most efficient form would have all the branches extending out about the same amount with the leaves at the end forming a sheet facing out. I'm sure it wouldn't be difficult to evolve that way if it were actually best, but if you look under tree you'll see they are nothing like that. Why aren't trees more like that? Dmcq (talk) 18:37, 15 July 2008 (UTC)[reply]
This is going to sound really snarky, but a short answer would be because intelligent design is probably wrong. That is to say, you're correct, that probably would be the most efficient arrangement. However, as you correctly identify, evolution has not yet favored that particular growth pattern. Its almost assuredly not impossible. In fact, its even possible that trees are approaching that kind of an arrangement. But they have to get there incrementally. Also, its entirely possible that the dome shape you imagine is not the most efficient, possibly for reasons of what the other trees in the area are shaped like (and therefore what spaces are available) etc. EagleFalconn (talk) 19:00, 15 July 2008 (UTC)[reply]
Thanks everybody for the replies, lots of ideas there. Nothing I could even begin to thinking of doing something like running a simulation with, especially by intelligent design I'd have to be God to be really sure my design was intelligent! I guess trees are quite different from each other so there can't be a unique best solution. On the point of whether tree have had enough time to evolve this, if you have a look at umbel you'll see something like what I was thinking about for flowers but even small plants don't seem to do this with their leaves. By the way the picture on the right of the carrot flower directly contradicts the text about the stalks being the same length. ;-) Dmcq (talk) 21:45, 15 July 2008 (UTC)[reply]
A dome would have gaps between the leaves, by having a three dimensional arrangement you fill in those gaps. There are certainly more efficient arrangements, but presumably they don't offer a large enough benefit, or have some downside, so trees haven't evolved that way. Trees have been around for 100s of millions of years, I think evolution would have achieved an optimal arrangement of leaves by now if such an obvious one existed. --Tango (talk) 19:28, 15 July 2008 (UTC)[reply]
Be interesting to know what the downsides might be. Perhaps it isn't best for leave to be in full sunlight and the top leaves are sacrificial to some extent, but then I guess they'd flop around or droop or something like that Dmcq (talk) 21:45, 15 July 2008 (UTC)[reply]
Trees probably don't grow according to centralized planning. Each little part of the tree is probably given a little autonomy in adapting best to its particular conditions. So you get something that looks a little irregular but is obviously efficient enough to work. That's all evolution gives you: just enough to work and not get totally out-competed. Anyway, your assumption about what is "optimal" is contingent on a number of assumed conditions about the particular light the tree could get, the spacing of trees between one another, wind conditions, the "cost" to the tree in terms of generating leaves, etc. I'm not sure your design would be ideally optimal in all conditions (and the question of how the tree would "know" how big to make each branch also probably introduces some sort of need for an energy-intensive feedback system as well). --140.247.241.142 (talk) 19:32, 15 July 2008 (UTC)[reply]
This answer and the next seem to directly contradict each other as to a cause to get the same result! And I can't make my mind up as to which one sounds more probable. Yes the individual leaves probably do compete with each other. And yes the whole tree might benefit and so be more successful if leaves cooperated in letting light through. I tend a little bit more to the former. As to a feedback system for knowing how much to grow and when to stop - tat would be fairly straightforward I'd have thought. Just keep growing whilst the light flickered a lot.~~
The sun moves.. Leaving gaps between the leaves means that leaves on the far side of the plant still receive light even when the light comes from the other side.. Also the wind moves the leaves around meaning that this sort of built in margin for error is useful.87.102.86.73 (talk) 19:51, 15 July 2008 (UTC)[reply]
See last question and answer, this assumes it is in the best interest of the tree to share the light around. I'm not ure that is right becaue it also allows light to fall below the tree and o allows compeitors to grow.Dmcq (talk) 23:21, 15 July 2008 (UTC)[reply]
Not sure the shape has anything to do with being efficient at using resources to gain energy from the sun. More like cutting down the problems caused by the sun.Dmcq (talk) 23:21, 15 July 2008 (UTC)[reply]
Yes, very interesting. They are much more like what I was thinking of. However they use up an awful number of branches to achieve the effect. Less branches with ends that opened out like the picture on the right in the article on umbels to hold the leaves would enable them to grow bigger with less expenditure on branches I'd have thought. Dmcq (talk) 23:21, 15 July 2008 (UTC)[reply]
The shape of a tree is a compromise between many different factors. A spherical tree such as a cactus is best for water retention, but this comes at a cost in photosynthesis efficiency (half the surface is shaded at all times). Big leaves are great for gathering sunlight, but are highly flammable, succeptible to wind damage, and leak water like a sieve. Pine needles are wind-resistant, burn without generating much heat, and are fast to regrow after a fire, but don't gather much sunlight.
It's funny that pine grow more in cold conditions if their leaves are bad at collecting sunlight. Trees seem to be just plain ornery. Dmcq (talk) 23:21, 15 July 2008 (UTC)[reply]
Like I said, it's a compromise. Pine needles aren't that great at gathering sunlight, but they are easy to replace, they burn without damaging the tree much, they aren't damaged by high winds, and they shed snow easily. A big-leaf tree might gather more sunlight, but that doesn't help much if the leaves get ripped off or burned on a regular basis. --Carnildo (talk) 22:53, 16 July 2008 (UTC)[reply]
There is no single "best" tree shape. Evolution ensures that any given tree species is near-optimal for its enviroment, but the wide range of environments and the number of different ways of responding to them means that there are many different shapes for trees. --Carnildo (talk) 22:28, 15 July 2008 (UTC)[reply]
Who knows? Perhaps there is a best tree shape or at lease a very much more restricted number of shapes that are optimal for their conditions than are anywhere near what happens in nature. I don't think I'm anywhere near perfect and yet evolution designed me (Go on, contradict me. No - oh well!). I guess the question I put does go somewhat towards asking what is an efficient tree shape, after all my thoughts about that were obviously wrong. Dmcq (talk) 23:21, 15 July 2008 (UTC)[reply]
Building on the answer above that they may just not have had time to evolve a shape like I was thinking: Fractal shapes can give something that looks like a tree, perhaps the answer that they are good enough for the job because they only compete with other trees is right, and they just haven't the need or maybe even the capacity to develop enough additional complexity to be other than a simple fractal. Dmcq (talk) 23:21, 15 July 2008 (UTC)[reply]
I think a big part of it is that a sphere may not be as effecient as you think. A sphere is effecient for containint volume and MINIMIZING surface area. It's in the benefit of the plant to maximize the surface area (and therefore the number) of leaves facing the sun. Also, by having a broken, tiered surface as most trees have, light gets to almost all sides and levels of the tree at any given time, so every area that needs food (for the most part) gets it. If it was just a big bag of leaf material draped over the tree, the further one gets from the equator the less light would be received by the tree: a large section of leaves would never see direct sunlight because of the earth's tilt. Of course, as 87.102 pointed out, with all the diversity in the world, there certainly are plants that sort of fit your idea. --Shaggorama (talk) 12:08, 16 July 2008 (UTC)[reply]
Well, more than one leaf facing the same direction when one leaf is occluding the other doesn't really give the tree the benefit of the full surface area of each; what needs to be maximized is the total amount of light being absorbed by the leaves. A single "bag of leaf material" would be easily torn by wind; with multiple layers the inner layers wouldn't be self-sustaining, so we have the present "design" as the most effective compromise. --Random832 (contribs) 17:01, 17 July 2008 (UTC)[reply]
I think we need to not imagine a lone tree on a hilltop, but a young tree trying to establish itself in the middle of a forest. A dome would be inefficient in that scenario. APL (talk) 13:02, 16 July 2008 (UTC)[reply]
there's also an ecological/evolutionary component. i.e. (as i was taught, can't verify it from my experience) trees which grow in dense forests tend to have a canopy of leaves which grab all the light, for purposes of competition. if they don't, another tree will, leaving them in the dark. on the other hand, trees which tend to grow less densely tend to have canopies which let much more light through, because any advantage to the individual tree is overshadowed by the advantage to the tree's progeny growing near the parent of getting some light through. this was supposed to explain why some leaves are so serrated, etc., and why some are huge elephant ear leaves and some are just little things. Gzuckier (talk) 19:33, 16 July 2008 (UTC)[reply]
Wind damage can take out whole limbs, as can a number of other factors. Leaves can be eaten away by anything from giraffes to bugs. It makes sense for a tree's branch structure and leaves to take on forms that can survive the whatever is likely to cause damage. The human body, likewise, seems to have all kinds of redundancy. Pfly (talk) 05:04, 17 July 2008 (UTC)[reply]
I had a look at forest and the trees there didn't seem to have a flat top unlike what I would expect. But having a look round at other trees under baobab and cypress there are lone trees with the sort of flat top I would expect in a forest. The dragon tree is more rounded at the top, the start of quite a good dome shape. It has quite thick branches though. The wind damage idea sounds interesting, I guess there might be less wind resistance with gaps for the wind to go through so branches an be thinner. Dmcq (talk) 10:54, 18 July 2008 (UTC)[reply]
wearing glasses
while wearing glasses may help a person suffering from myopia by focussing rays from objects on the retina, wont it alter the relative distance of the object from the eye? for instance an object at infinity will appear to be at the focal point of the lens. so do objects appear closer/further than they actually are?
59.180.19.237 (talk) 20:43, 15 July 2008 (UTC)[reply]
As someone who wears glasses for somewhat severe nearsightedness I can tell you that it takes about a day or two to get used to the change in depth perception caused by a stronger prescription. During those one or two days I find myself reaching for things about an inch closer than they really are.
Per APL, objects do indeed appear to be in the 'wrong' place in space—at least, at first. The brain very rapidly adapts to the 'distorted' view, and you can start to confidently reach for your pints once again. I don't have a link for you, but studies have been done involving the use of glasses which deliberately distort vision (including going so far as to invert vision: [9]). Depending on the degree of distortion, subjects were able to perform tasks relatively normally after a period of acclimatization (hours or days). The brain is quite adept at integrating the feedback from the body's musculoskeletal system with vision information to build a consistent internal model of reality. TenOfAllTrades(talk) 21:18, 15 July 2008 (UTC)[reply]
thanks. but what i dont understand is, in the case of a diverging lens, the image is always formed between lens and focal point(am i right?)-so even very far off objects will appear to be at the focus. so does that mean that people wearing glasses perceive everything to be within the focal length of the lens?
59.180.73.240 (talk) 04:44, 16 July 2008 (UTC)[reply]
effectively yes, I think you're right - this is true for people with short sight - and the image should be within the range in which they can see ie near things.87.102.86.73 (talk) 11:12, 16 July 2008 (UTC)[reply]
It sounds like you have been studying optics, particularly thin lenses - so that's good. Just a small misunderstanding I think. Keep in mind, the lenses in our eyes take incoming light and focus it onto the retina. The image distance is always the distance between the lens and the retina - so pretty constant. The way we do this is by changing the shape (and thefore the focal length) of our lens. For many people, our lenses do not quite focus the light correctly and the light is focused too soon or too late. That is why corrective lenses are used, they cause the light to be focused directly on the retina. If the eye tends to focus the light too early, we use diverging lenses to spread it slightly so it focuses later, etc. So objects don't 'appear' to be hovering at the focal point of the lens in front of us anymore than the original object does. The image is not in front of us - it is on our retina. Hope this helps. PhySusie (talk) 11:23, 16 July 2008 (UTC)[reply]
I think what you're looking for is virtual image. On a slight tangent from the question, I can't find a source for this but an experiment was once described to me where a group of people were given glasses that inverted their visual field, and after a day or two they all adjusted so that when the glasses were removed, they saw everything upside. The brain's a neat thing/ --Shaggorama (talk) 15:53, 18 July 2008 (UTC)[reply]
July 16
astronomy
our solar system is laid out like a plate is it likely that the planets are spin offs from our sun at its birth
dose the sun rotate ?
what is the cause of gravity?
why do the planets rotate anti clockwise?
what is the force that makes the planets travel along the same path around the sun with the same speed all the time ?
do all the stars which are suns all have planets?
where in the milky way is our solar system located?
these questions have been something i have been wondering about for sometime.
If you make even the feeblest attempt at finding these answers yourself, others will be happy to fill in any gaps in the information already easily available throughout Wikipedia. -- kainaw™03:22, 16 July 2008 (UTC)[reply]
I'll bite. Quick and simple laymans answers. For more detailed answers, checkout the relevant articles.
The planets were formed from the accretion disk that surrounded the proto-star that eventually became our sun.
Yes.
General Relativity explains gravity. Any object that has mass, will make a dent in space-time. The larger the mass, the greater the dent. The greater the dent, the greater the force of gravity.
Because of conservation of angular momentum. When the solar system was formed, the accretion disk was spinning in that direction. Venus spins the other way because a massive asteroid collided with it, and changed its rotation direction.
Szeretetelchak, your curiosity is to be commended, but your questions betray some hidden assumptions, which you need to examine more closely.
"Our solar system is laid out like a plate ..." - is it really ? Although the orbits of the major planets lie approximately in the same plane, there is much more to the solar system than the planets. For example, the outer Oort cloud, which contains contain several trillion individual comet nuclei, is spherical, not "plate shaped".
"What is the cause of gravity ?" - simple answer is mass, but this begs the question "What is the cause of mass". Answer that one, and you are in the running for a Nobel prize (unless Peter Higgs beats you to it).
"Why do the planets rotate anti clockwise ?" - there are two misconceptions here: (1) the sense of rotation depends on where you are looking from and (2) even looking from one direction, not all of the planets do rotate in the same sense. But you may be confusing rotation with orbital revolution.
"What is the force that makes the planets travel along the same path around the sun with the same speed all the time ?" - a planet does not travel with the same speed all the time. Aristotle believed this, but he was wrong - see Kepler's laws of planetary motion, especially the second law. And a planet does not even retrace exactly the same orbit relative to the sun, due to orbital precession.
"Where in the milky way is our solar system located ?" - the solar system is not located at a single place in the Milky Way - it is travelling at a speed of about 220 km/s relative to the Galactic Centre, and it has complete about 20 orbits around the Milky Way since it was formed. It is more meaningful to think about the characteristics of the solar system's orbit within the Milky Way.
Anyone know what's happening here? The raptors don't actually seem to be seriously trying to kill each other (with that beak, it wouldn't take long to inflict a fatal wound) - one just seems intent on pinning the other to the ground and keeping him/her there. --Kurt Shaped Box (talk) 06:56, 16 July 2008 (UTC)[reply]
Take note that most animals do not try to kill other members of their own species. Animals that happily and routinely kill other species are usually much more likely to intimidate or submit when among their own. (Humans are often an exception to this.) --140.247.240.177 (talk) 20:02, 16 July 2008 (UTC)[reply]
Outside of military/politically-motivated/gang/revenge situations (what I would refer to as 'violence with purpose'), the vast majority of humans scraps and scuffles have a non-lethal conclusion. Take your typical post-bar-closing scraps. Statistically, very few result in one human beating another human to death with his/her bare hands (obviously, all bets are off when guns and knives come into play). No, the battle seems to end when one combatant is a bloody, broken mess and unable to continue. It takes more will than most people posses to continue to beat and kick a man once he stops moving... --Kurt Shaped Box (talk) 23:59, 16 July 2008 (UTC)[reply]
Size of the Internet
What's the size of the Internet? Number of gigabytes sent/stored, number of computers used, number of human users, amount of power consumed daily, etc? —Preceding unsigned comment added by 24.7.54.224 (talk) 08:43, 16 July 2008 (UTC)[reply]
An interesting question, I expect there is not going to be a precise answer but I'm sure others at this desk will be able to come up with something. In terms of human users, the article Demographics of the Internet may be of interest to you. Jdrewitt (talk) 09:28, 16 July 2008 (UTC)[reply]
Google is said to process over 20 petabytes (20 million gigabytes) data per day. Obviously, this doesn't really help a lot in getting stats about the internet as a whole. Still darn impressive, though. -- Aeluwas (talk) 11:07, 16 July 2008 (UTC)[reply]
The problem is that the internet is a system, not a thing. Every computer connected to the internet is, for that time, part of the internet. Computers connect/disconnect all the time. This question is similar to asking "How many people are in McDonalds?" It cannot be answered because the number of people change every second of every day. -- kainaw™11:47, 16 July 2008 (UTC)[reply]
But you could do a reasonable Fermi estimate to get in the right order of magnitude. Just because something has regular fluctuations doesn't mean it isn't mostly stable to a certain degree of accuracy. The population changes every day but we still have a census that is meaningful. --98.217.8.46 (talk) 14:06, 16 July 2008 (UTC)[reply]
One of the differences here (and in the McDonalds case) is that the change is likely not close to being constant. Americans still make up a big percentage of internet users despite rises in China etc. And people in developed countries probably have bigger hard drives and more data in general then those in the developing world, probably more power hungry computers (although hard to say given the recent move towards energy efficiecy). Therefore, at peaks times for American connection your going to get a large increase in the overall in the data content. I suspect weekends have even more (on the other hand, businesses are more likely to have their computers offline on the weekends and at night time). Similarly in McDonalds, people don't tend to eat at all hours of the day. And I suspect Americans make up a big percentage of McDonalds customers. The number of people in McDonalds in the world, at say 5-8 p.m. (in the various timezones) in the US is going to quite a bit higher then at 3 a.m. in the US. Again weekends and I suspect public holidays are going to be even higher. While I have no specific evidence, my gut feeling is both the data and particularly the number of people of McDonalds at any given time in a day can vary by a large percentage (say 95%+ for McDonalds) and obviously by even more when we consider over the various days of a year. On the other hand, I suspect population figures in any given country under normal times don't tend to vary by even 1% (for the US this is over 3 million) ignoring overall growth/decline. It would be better in both cases (McDonalds and internet) to think in terms of averages over a time interval (say average per/day). (Another issue of course is what is a computer? Is a Wii? A mobile phone? A router? A fridge? And if I have a P2P app in the background while playing a non online game am I using the internet? What about if I'm occasionally messaging a friend online?) Nil Einne (talk) 17:21, 16 July 2008 (UTC)[reply]
I think Nil has it exactly right that the internet as we conceive it has to be looked at as a system in flux. I suppose there's some way of estimating the amount of data stored on all the servers, but it would be a poor estimate for a whole host of reasons. To name only one of the most obvious, a media file that no one has uploaded or downloaded in months might count for just as much as some hot video on YouTube seen by millions a day. I disagree, however, that we have to work at defining a computer; all we need to measure is traffic; I don't think it really matters what device is doing the uploading or downloading. If we stick with the traffic definition, Nil's P2P app would simply contribute to the download or upload quantity. Matt Deres (talk) 18:42, 16 July 2008 (UTC)[reply]
If it is asking for any advice on treatment, diagnosis or signs and symptoms (the latter is my opinion) then it is a request for medical advice. The specifics, such as the effects of Citirizine, are irrelevant :) —CycloneNimrodTalk?06:36, 17 July 2008 (UTC)[reply]
An inter-fabric-of-cosmos-wormhole/grayhole
Today while I was exercising I thought that in a supermassive blackhole, the fabric of cosmos might break, and the matter will just swarm to the other side of the fabric of cosmos, and warp timespace oppositely by warping on the opposite side of the fabric of cosmos. As the warp builds, it might create a black hole on the other side, which is equivalent to a white hole on our side though no mass is on our side of the fabric of cosmos the place of black hole there(a zero mass black hole(zero mass black holes also act like white holes)). But, due to the hole created by the supermassive blackhole mentioned in the first line will make the matter swarm to the other side and again and again and again... But another thought is that only half of the matter will swarm to the other side, but the fabric of cosmos cannot warp due to having equal mass on both sides and either stabilizing the warp or the fabric of cosmos spiting in half, and having created a new universe with the new half. Still, another thought lead me to thinking the hole will create a big bang on the other side with the matter spreading out, like the big bang, and matter continuely falling over the other side and after half of the matter falls to the other side, pressure will slow down the transfer, but the trend remains. After all the matter flows there, it might ignite a new big bang on the opposite side once again. Or perhaps the matter will equalize and.. the possibilities are infinite. Could such phenomena happen? please reply!!! —Preceding unsigned comment added by Superwj5 (talk • contribs) 12:21, 16 July 2008 (UTC)[reply]
Please see black hole and white hole. This is a reference desk, not a "tell me if my most recent theory is valid" desk. You appear to be in need of a discussion forum. There are thousands (if not millions) of them on the Internet. This is not one. -- kainaw™12:35, 16 July 2008 (UTC)[reply]
It sounds like you're thinking of the universe as a rubber sheet being warped by massive objects, which is a good analogy up to a point, but isn't entirely accurate. There isn't really an "other side" to the universe where massive objects would push the universe in the other direction, at least not in a standard interpretation of general relativity (M-theory might have something along those lines, I've never studied it). --Tango (talk) 22:17, 16 July 2008 (UTC)[reply]
I have fallen for the marketing tactics - i've bought myself an energy-drink in anticipation of 'cup finals' night at my local football thing tonight. Putting to one side the question of whether energy-drinks produce any increase amount of energy/stamina does anybody know how long before said game is 'optimum' for drinking said energy drink? E.g. Before I play I use my inhaler about 30 mins before (as directed by my asthma nurse) and that tends to mean I don't need to use it during the game. Should I drink my drink 10 mins before, 30 mins, an hour, 2 hours? Granted I don't believe these have a 'major' impact but given that i've bought the drink already I might as well try drink it at the best time possible.
I ask because i'm thinking whatever is in the drink (sugar and chemicals no doubt) needs time to 'work' or be 'digested' or something. Any help greatly appreciated. 194.221.133.226 (talk) 13:17, 16 July 2008 (UTC)[reply]
They are pretty much sugar-water, with maybe some caffeine tossed in. Since sugar is rapidly digested, I'd drink it right before. There is also the "sugar crash" to consider, which will cause you to rapidly lose energy as soon as the sugar rush is countered by your own insulin production. Starches are usually suggested to be eaten with sugar, since they are digested a bit slower, and then hold blood sugar steady when it would otherwise crash. Protein and then fats are good for even longer terms. StuRat (talk) 14:13, 16 July 2008 (UTC)[reply]
In most energy drinks, it is not caffeine that provides energy. Caffeine simply helps to bypass your body's feeling of fatigue and helps keep you awake. That is of course a benefit to someone who needs to stay up late working. The energy that you need to be more active is provided by, as StuRat said, sugar (ususally glucose or dextrose, I think it's the former in Lucozade). This is digested very early on and doesn't go through the entire small intestine, as you would expect larger proteins and lipids to do. Energy drinks also contain taurine which helps to do a lot of things but in energy drinks it's particularly helpful due to it's effects of countering osmotic shock (good if you're an athlete) and it's role of being a surfactant of the cholic acid conjugate.
Basically, I recommend you'd drink your energy drink about 10-15 minutes before the game. This should mean it's starting to be digested roughly as the game starts and should give you a pretty optimum time with a 'sugar high' before the crash. — CycloneNimrodTalk?15:31, 16 July 2008 (UTC)[reply]
It also ensures that you're on the loo just when the quarterback makes that fantastic throw right to the runner in the end zone while the cheerleaders flash the other team. Or you keep the empty bottle handy ;-). --Stephan Schulz (talk) 00:19, 17 July 2008 (UTC)[reply]
Why do birds move their heads in discrete amounts rather than in smooth and continuous motions as mammals do? They look almost like they're in stop-motion. I can explain further if you don't know what I mean. --Sean13:22, 16 July 2008 (UTC)[reply]
I believe they have optical processing in the brain that enables them to easily spot moving objects against a still background (we have this ability, too). This works better if the head is held still to prevent apparent background motion. So, they hold their head still for a bit then quickly move it to the new position for another "snapshot", while walking. This might bring up the question "why don't humans do this ?". Our heads and brains are too big, such that repeated, quick, jerky motions like this would make us dizzy and/or cause us brain injury (although we might hold our head still while trying to spot a small object moving in the distance). So, apparently there is at least one advantage to having a bird brain. StuRat (talk) 13:43, 16 July 2008 (UTC)[reply]
You may want to read the saccade article. My guess is that since the eye motion amplitude in birds is somewhat limited (or sometimes very limited, as in barn owl), rapid head rotations are actually saccades. --Dr Dima (talk) 13:52, 16 July 2008 (UTC)[reply]
There are four reasons:
1. Balance
2. To achieve depth perception through their (virtually) monocular vision
3. To read a stable image from their sub-standard eyes
For "why don't humans do it"... We have depth perception without jerking our heads from side to side. If you lost one of your eyes, you may jerk side to side more to get a sense of depth - and likely become rather accustomed to overlaying something you just saw onto something you currently see - just like a chicken. -- kainaw™14:53, 16 July 2008 (UTC)[reply]
Most birds eyes are located on the sides of their heads, permitting them to see over 300 degrees without moving. However, the disadvantage of this positioning is that movement produces motion parallax errors - objects nearby appear to move faster than objects further away. To preserve visual acuity, a bird will lock its head in position whilst moving its body beneath it. It will then move its head to the next 'lock' position, which it again holds. In this way the parallax effects are minimized. Incidentally, the combined action of "head locking" with walking gives certain birds (such as pigeons) the characteristic nodding appearance. See here and here for in depth studies. Rockpocket20:33, 26 October 2007 (UTC)[reply]
So, why don't all birds do this? Gulls (just to use an example I'm familiar with) have eyes placed at the side, yet they walk with a straight neck. --Kurt Shaped Box (talk) 22:56, 16 July 2008 (UTC)[reply]
Good question. According to the second source, "This behaviour occurs in at least 8 of the 27 orders of birds including relatively common species such as pigeons, doves, hens, starlings, pheasants, coots, rails, sand-pipers, phallaropes, parrots, magpies and quail." So why not the others? Well, it might be something to do with the neural architecture of the visual system, or it could be do with ecology, or both. It appears to me that most of those listed above would have predators and it might in in their interest to have an ability to watch out for them with good visual acuity. Bird without natural predators may not have the same requirement. This is purely speculative, though. Rockpocket18:48, 17 July 2008 (UTC)[reply]
i have searched for information on ABSOULUTE POSITION. that is, to be stationary (say, outside the universe) I would like to know (1) If this is possible, and (2) What would be observed' —Preceding unsigned comment added by 86.158.32.65 (talk) 22:13, 16 July 2008 (UTC)[reply]
I'm no astrophysicist but i'm pretty sure we don't know anything about what is outside the universe, certainly not if it's possible to go there or not. —CycloneNimrodTalk?22:18, 16 July 2008 (UTC)[reply]
By definition, the universe incorporates everything that exists. If there are other universes with their own scientific laws, constants, or events (see many-worlds interpretation), its inhabitants would be unable to observe us and we would be unable to observe them.
One exotic method of travelling to universes is via wormholes, which require the existance of black holes with no mass. There are two problems with this: (1) black holes are the result of the collapse of massive stars, and (2) any theoretical black hole with no mass would cease to be a vacuum when matter contacts it. --Bowlhover (talk) 23:59, 16 July 2008 (UTC)[reply]
specifically, the recommendation to use DOVE brand soap, which is 1/4 moisterizer, just seems wrong. here is a list of ingredients mine lists: sodium lauroyl isethionate; stearic acid; sodium palmitate; aqua; lauric acid; sodium isethionate; sodium stearate; cocamidopropyl betaine; sodium palm kernelate; parfum; glycerin; sodium chloride; zinc oxide; citric acid; tetrasodium EDTA; tetrasodium etidronate; alumina; alpha-isomethyl ionone; benzyl alcohol; butylphenyl methylpropional; citronellol; coumarin; hexyl cinnamal; limonene; linalool. cl 77891. I'm not asking for medical or dental advice, but couldn't someone brushing their teeth with that stuff like, get, aluminum poisoning or something? Are any of those ingredients toxic or otherwise harmful? Wouldn't they, at a minimum, wear down the tooth enamel? surely it's no substitute for toothpaste, and even if it's true that "brushing your teeth with a regular unscented bar soap can kill all germs and remove all plaque and tartar that ordinary tooth paste cannot remove" surely there must be something equally negative about it, such as I don't know getting poisoned, or losing your tooth enamel. Otherwise why wouldn't toothpaste just have that stuff to begin with? I am emphatically not asking for medical, dental, or legal advice, just curious what the science behind that might be... —Preceding unsigned comment added by 83.199.57.103 (talk) 22:52, 16 July 2008 (UTC)[reply]
It is very hard for human digestion to absorb aluminium, particularly from something insoluble like alumina. Those that are poisoned by aluminium, usually have it introduced to the blood. You will find that toothpaste can have some of those ingredients, and can make similar claims to removing plaque. The soap probably tastes horrible. Graeme Bartlett (talk) 23:09, 16 July 2008 (UTC)[reply]
The concern about aluminum, in recent years, has not been so much about acute aluminum poisoning as about the fact that aluminum has been found in the plaques in the brains of Alzheimer's patients. As I understand it, this concern has dissipated somewhat with the failure of researchers to find any direct causitive, connection, but the jury still seems to be out: this article asserts
While a direct causal role for aluminum or other transition metals (copper, zinc, iron) in AD has not yet been definitively demonstrated, epidemiological evidence suggests that elevated levels of these metals in the brain may be linked to the development or progression of AD.
are you guys telling me that despite being 25% moisterizer if the ingredients are as above, they shouldn't be harmful to use in place of toothpaste? What about my enamel question?
I'm not telling you anything of the sort. I mostly responded to get the correct spelling of aluminum into the text as many times as possible. Because that's how aluminum is spelled, you know. Aluminum. --Trovatore (talk) 23:42, 16 July 2008 (UTC)[reply]
Aluminium is a silly word; aluminum as derived from alumina was just fine, until someone decided to add the spurious i. Who knows how much platinium someone paid to IUPAC to pick the wrong spelling, but they have no authority. --Trovatore (talk) 23:56, 16 July 2008 (UTC)[reply]
Pah! I won't accept it. It may take another millenum before I can ententan such a thng! -) (a smiley without spurious 'i's). Seriously though, spelling differences are interesting, and Alumin(i)um has an interesting history in that regard. Fribbler (talk) 00:04, 17 July 2008 (UTC)[reply]
Common sense says it should be aluminum, as derived from alumina. Consistency with what? There are other element names that end in um -- platinum, tantalum. --Trovatore (talk) 17:18, 17 July 2008 (UTC)[reply]
But far more with ium, Americium, Barium, Berkelium, Beryllium, Bohrium, Cadmium, Caesium, Calcium, Californium, Cerium, Chromium, ... I'm now getting bored, but you get the picture, about half of all element names end in '-ium' and all recently named ones do, so this suggest convention is in favour of an 'ium' ending, with those without being the spurius early discoveries for which there was no naming convention. Aluminium QED. Philc 0780 11:32, 18 July 2008 (UTC)
No, that's completely wrong. Aluminum is just what you get when you change alumina from first declension feminine (or second neuter plural) to second declension neuter singular. Simple, clean, obvious.
As I say, alumium (derived from alum rather than alumina) would also have been OK, but it didn't win out, whereas aluminum did, in the dialect of English spoken by more than 60% of first-language speakers worldwide, namely North American English. --Trovatore (talk) 15:48, 18 July 2008 (UTC)[reply]
I checked out the interwiki links of Aluminium, and I didn't find ONE single language, except for English, that calls it Aluminum or similar. Almost all entries using our writing systems have it ending with "-inium". :-) Aeluwas (talk) 13:35, 17 July 2008 (UTC)[reply]
So what? It was discovered hmm--not quite "discovered" maybe; "first named" anyway by an English speaker, and he called it aluminum (well, first he called it alumium, which would also have been OK, but it doesn't seem to be a contender anymore). --Trovatore (talk) 17:18, 17 July 2008 (UTC)[reply]
Well, they're deliberately using a product for a purpose it is not meant for, and has probably not been tested as safe for. They're also foregoing the aspects of toothpaste that are known to be beneficial—the fluoride compounds. And they're justifying it based on ad hoc ideas about the benefits of anti-bacterial soap should affect their mouth (which they know nothing about—there are many types of helpful bacteria in the human body, and rampantly introducing anti-bacterial agents into different parts of it is not a great idea), and rumors about toothpaste (evil glycerin etc.), and then justifying it not with systematic testing, but confirmation bias-rich anecdotes. So yeah, in my book they're doing a few things wrong, a priori. I mean, science ain't perfect, and for that matter neither are regulatory agencies, but I trust them a lot more than some anonymous yokels on the internet and their folk medicine. --98.217.8.46 (talk) 00:10, 17 July 2008 (UTC)[reply]
Toothpaste and soap differ in detergent content--it's the main ingredient in any soap. Detergents can contribute to wear of dentine[11] and soap can reduce the strength of dentine bonding agents[12]. These people may experience a subjective benefit, but I couldn't readily find anything in PubMed that would suggest that this is an idea currently studied or recommended by the dental community, but these two studies indicate potential problems to worry about with this technique (beyond the aforementioned lack of safety testing & no fluoride benefit). — Scientizzle17:51, 17 July 2008 (UTC)[reply]
is there a distance where eye focus and binocular effect disappears?
Is there a distance at which no normal person can tell, without moving their head for parallex effect, whether there is a poster (for example) at that distance or, for example, a mountain hundreds of miles further, because the focus and binocular effect have become imperceivable? Sorry for the awkward phrasing, I think you get what I mean and you're welcome to offer to a better phrasing.—Preceding unsigned comment added by 83.199.57.103 (talk) 22:39, 16 July 2008 (UTC)[reply]
Yes and no. Somewhere around 20-50 feet away, binocular cues start being useless for depth perception, but the brain uses many other techniques as well. You might be interested in the article depth perception and the articles linked from the "monocular cues" and "binocular and oculomotor cues" sections. --Carnildo (talk) 23:22, 16 July 2008 (UTC)[reply]
Yes, because compared to the size of a human eye's lens, 20-50 feet is almost an infinite distance. Imagine a point source of light at 7 m with the middle of the lens directly facing it. Since the source's image on the retina must also be a point, the lens refracts all light rays onto the centre of the retina. 5 mm from the lens' centre, light from the source is bent by 0.04 + x degrees; a refraction of 0.04 degrees would cause the light ray to be perpendicular to the retina, while an additional x degrees is needed for the ray to hit the retina's centre. Rays from an infinitely-distant source are refracted by x degrees, where is only 0.04 degrees less than the source at 7 m.
As for the binocular effect, the distance between the eyes is 5 cm. The angular positions of a 20-ft-distant object that the eyes report differ by 0.6 degrees, which is the angular diameter of the Sun--probably large enough to notice. 30 m is the distance at which an object's apparent positions differ by 0.1 degrees, so I would say the binocular effect absolutely cannot be used at greater distances. --Bowlhover (talk) 01:08, 17 July 2008 (UTC)[reply]
This is just anecdotal, but it relates to the question, so I'll tell the story. I wear glasses for myopia. One time years ago I got a new prescription for slightly stronger glasses. I put them on in the optician's office and they seemed fine. I then stepped outside and discovered that most of the world had become flat: nothing was farther than 20 feet away! I was traveling by public transit and next had to cross a 4-lane street to get to my stop, and crossing the street with that illusion in place was downright surreal. The cause, of course, was that with the old prescription my eyes had been unable to quite focus at infinity -- and my brain had learned to use this as a distance cue! Anything that's in sharp focus, it had learned, must be 20 feet away if binocular vision doesn't say it's closer.
Fortunately, the brain adapts well; the effect faded within an hour. --Anonymous, 05:30 UTC, July 17, 2008.
Another anecdote. I've found that looking at photos with a significant depth (it works better with some then with others) with one eye gives them an almost 3D look. Obviously with no binocular vision, the brain starts to look at other clues more and you see depth that isn't there Nil Einne (talk) 11:19, 17 July 2008 (UTC)[reply]
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
|
-0-S2+-O-
|
OH
2. OH
|
0=S=O
|
OH
3. O
↑
H0-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 [13], [14], and [15], 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 [16]).
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]
Chicxulub & the Deccan Traps: Antipodal Connection?
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]
Funny feeling in your forehead
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]
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]
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]
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[17][18]. 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]
Electromagnetic hover thingy
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).
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]
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]
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]
: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]
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]
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]
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]
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 [19]. 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]
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]
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. [20] which suggests a lower survival rate in Chinese women) Nil Einne (talk) 07:24, 19 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]
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:[21]. 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]
![[1]](/wiki/Image:Ameisen.jpg){kind=link}
![[21]](/wiki/Image:Carboxylic_acid_dimers.png){kind=link}