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October 26

Benzodrene

In The Diary (Freaks and Geeks episode), one of the characters says that Kerouac was high on "Benzodrene" when he wrote On the Road (something our article disputes).. but I can't find any information on Benzodrene, and only 30 google results. Is this a simple misspelling? I uploaded the relevant clip to youtube. (I guess in the 1980s they still took the beat generation somewhat seriously for some reason..)--ffroth 07:12, 26 October 2007 (UTC)

I think she actually said, "Benzedrine" Rockpocket 07:32, 26 October 2007 (UTC)

Ohh thanks --ffroth 13:49, 26 October 2007 (UTC)

UK - Safest place to live in the world?

I'm leaving aside all man-made aspects of danger here. I'm thinking that maybe the UK is one of the safest places to live in the world when it comes to nature viz :-

We don't get major natural disasters. There are no volcanos. Earthquakes are extremely uncommon and very rarely cause fatalities. We don't get hurricanes. We get occasional tornadoes and high winds but compared to say the USA they are nothing. The temperature rarely gets high enough or low enough to kill you easily. We have exactly ONE species of poisonous fauna - the adder which isn't even all that poisonous - no spiders or scorpions. No dangerous carnivores (barring the odd escaped panther?) - bears and wolves were wiped out. Is there some kind of index for the relative danger from the natural environment by country? Exxolon 13:21, 26 October 2007 (UTC)

Like you mentioned, you are leaving out all the dangers caused by man, which are far more dangerous than any natural disaster. 64.236.121.129 14:25, 26 October 2007 (UTC)

We don't have guns either...or 'militia' groups or KKK members or crazy religious groups who wall themselves off in large compounds and arm themselves to the teeth. On the other hand, we do have terrorist attacks that are more frequent than in the USA (for example). I'm sure there are safer places - but safety isn't everything. Theres jobs, standard of living, friends and family. I'm sure you could find a desert island somewhere with NO risks at all - but what would life be like? SteveBaker 18:20, 26 October 2007 (UTC)

Be fair, our crazy armed hermits are dangerous mainly to government agents who come in shooting unannounced, and our other armed cranks are dangerous mainly in places where guns are forbidden. —Tamfang 22:14, 29 October 2007 (UTC)

Ireland may be even safer - we don't have adders or wildcats, and never get tornadoes or even heavy snow, and have neither heatwaves (didn't it reach 40 degrees last summer in Cornwall?) nor the extreme cold of Scottish winter. EamonnPKeane 15:03, 26 October 2007 (UTC)

We also don't have malaria-causing mosquitos, rabies or any other diseases that visitors to the the UK would need to be immunised against. The main natural threat has to be climate change (which partially happens naturally as well as being contributed to by man, many parts of the UK would be underwater if sea levels rose and if the transatlantic currents changed, it could drastically alter our climate. GaryReggae 19:33, 26 October 2007 (UTC)

Does 'cuisine' count as a major natural disaster? Mad Cow disease and hoof and mouth disease come to mind as the type of outbreaks that affect U.K disproprtionately. --DHeyward 06:34, 27 October 2007 (UTC)

Mad cow - okay, I'll give you that one. Foot and mouth, however is more of a financial thing for the farmers - it's not (very) communicable to humans and hardly a threat to life. --Kurt Shaped Box 07:13, 27 October 2007 (UTC)

Note that in each instance you're comparing the UK with the worst place. For example, for storms you compare with the USA. But you should be comparing with other places that get little wind. I don't know which that would be, but the Netherlands is sort of shielded by Britain and therefore gets less wind when there is a storm. Of course the Netherlands could get inundated much more severely during such a storm, such as in 1953, but we have fixed that problem since. :) Actually, Britain and Ireland are easy to keep free of dangerous animals because they are islands, but the Netherlands has so little nature left that we don't have anything worse than adders either. Or do we? What about lyme disease, spread by ticks? Doesn't the UK have that too? Speaking of diseases and islands, what about (yes, here it comes again) New Zealand? Almost totally free of dangerous animals and diseases. There is volcanic activity, but that isn't too severe. And it's just in specific areas. Does the entire country have to be safe? That would give big countries a disadvantage, but that's the wrong way around - a big country increases your chances of finding a safe area. DirkvdM 07:44, 27 October 2007(UTC)

UK has the fish n chips a major delicious health hazard. Aside from that why would the UK be safer than say eastern Europe if you only consider natural dangers? If the sea level rises how high and protected is london? Keria 16:56, 27 October 2007 (UTC)

Heh don't live in the North Island of New Zealand. Auckland you're basically living next to an overdue volcano, Wellington you're living directly on the boundary of two plates ready to grind, the Bay of Plenty area gets flooded easily, central areas get the same volcano issues (Mount Ruapehu is the most recent one). --antilived^{T | C | G} 21:04, 27 October 2007 (UTC)

Apropos of nothing, the United Kingdom actually has a higher "tornado density" than any other country in the world. For example, on November 21, 1981, 104 tornadoes hit the country during daylight hours alone. Of course, the overwhelming majority of them were virtually unnoticable. GeeJo ^(t)⁄_(c) • 11:25, 28 October 2007 (UTC)

The UK could be in big trouble if the shutdown of thermohaline circulation occurs. StuRat 19:47, 28 October 2007 (UTC)

Meh. Just a different type of weather for us to whine constantly about... :) --Kurt Shaped Box 22:32, 28 October 2007 (UTC)

The southern Appalachians are pretty good too -too high up for hurricanes, not flat enough for major tornadoes, not on a fault line, no volcanoes. The most dangerous animals are the rather wimpy copperheads (timber rattlesnakes stay at low elevations); black bears are really not dangerous as long as you don't screw with them. Also, the climate is very nice and the country is incredibly beautiful.

Also, the people are really quite nice in most parts, especially compared to Aa big city. 98.196.46.72 03:34, 1 November 2007 (UTC)

If you don't mind about the cold, what about Antarctica - there are almost no large animals at all, never mind dangerous ones. Apparently, the largest land animal in Antarctica is Belgica antarctica - a flightless midge which is 12mm across. I would imagine the risk of crime is also very minimal. 130.88.151.238 15:50, 1 November 2007 (UTC)

A bipedal molecule

This is not a very normal question, but I'm looking for a molecule that, when drawn as a diagram, looks like a human (or a stick figure, to be more precise). I understand that such a molecule may require one to overlook certain rules when it comes to drawing molecules, and I'm afraid my knowledge of drawing molecules is very basic, but it would be great if I could find the closest match to a human figure possible. So far, the closest I've come is allylbenzene, but it requires some manipulation of the molecule. Benzene does seem to make a great head for the figure, though. Any ideas would be greatly appreciated. Many thanks Vvitor 13:26, 26 October 2007 (UTC)

Nanoputian? It says that they've actually been synthesized. Also look at [1] (about halfway down the page) and [2] for the actual journal article. --Bennybp 14:22, 26 October 2007 (UTC)

That's absolutely fantastic! Thank you so much!Vvitor 15:07, 26 October 2007 (UTC)

Three characters of the One over zero webcomic are antropomorphic molecules. – b_jonas 09:45, 29 October 2007 (UTC)

additive nature of heats of reaction

what is it, what does it affect, and if you answer I will thank you. haha. --MKnight9989 14:35, 26 October 2007 (UTC)

Ah, there's a name for this, but I forget. It's the concept that the heat of reaction for A -> C equals the sum of the heats of reaction of the reactions A -> B and B -> C. This also applies to more complex chemical reactions, so long as the reactions you are adding have the same net products and reactants as the final reaction you're calculating the heat of. Someguy1221 17:01, 26 October 2007 (UTC)

Hess's law? —Keenan Pepper 17:37, 26 October 2007 (UTC)

Thanks guys.--MKnight9989 12:31, 30 October 2007 (UTC)

What is the name for this kind of aircraft, and why don't we make them?

http://images.wikia.com/starcraft/images/6/6e/Banchee.jpg

^Would something like that be considered a helicopter? Where you have two covered turbofans (I think they are turbofans), on either side of the body. The tail rotor doesn't make much sense though, because you can just have each turbofan spin in opposite directions... Anyway, why haven't we made an aircraft like that yet? It appears to be far superior to our helicopter designs where you just have one very larger rotor on top, and a tail rotor. This design looks stealthier, not as vulnerable, faster (if combined with a jet engine, which a regular helicopter can't use), doesn't need a tail rotor7, potentially can use ejection seats (which are impossible to mount on helicopters for obvious reasons), etc. Anyway I've seen lots of fictional designs that look like the example I gave, so why hasn't it been created in real life yet? 64.236.121.129 15:05, 26 October 2007 (UTC)

• Well, we do have the V-22 Osprey which sort of operates that way. Its history will show why we don't have more of them right now... Arakunem 15:26, 26 October 2007 (UTC)

That's not the same at all. That's a tiltrotor aircraft. It has nothing to do with what I'm talking about. 64.236.121.129 15:38, 26 October 2007 (UTC)

Tiltwing perhaps a little closer? Just because it appears in computer games doesn't actually mean that it is superior to actual helicopters. Perhaps designers simply enjoy the model rather than that of a typical helicopter model? I mean it does look more 'futuristic'. Can you quanitify how it is 'stealthier' or less vulnerable than a regular helicopter? Lanfear's Bane | t 15:46, 26 October 2007 (UTC)

No, Tiltwing has no relevance to this design either. Your second statement, is an assumption. My question is, if that is true, why is it not practical or better than existing helicopter designs. I'm assuming you aren't familiar with the Comanche helicopter. It has a shroud over its tail rotor to help reduce its radar signature. It of course, can not mount a shroud over its main rotor. However this design of aircraft can, and as a result, should help reduce its radar cross section far more, since it lacks the large main rotor, and tail rotor. It appears to be less vulnerable because it lacks a rather vulnerable main rotor. Two smaller turbofans mounted on the sides aren't as exposed to enemy fire. I'm not saying the design I posted is definitely practical or better than existing helicopter designs, I'm asking if it isn't, why? This question is directed to those who are familar with engineering, aviation, etc. 64.236.121.129 16:03, 26 October 2007 (UTC)

(ec)What you're talking about is a cartoon. The tiltrotors include actual, real aircraft. See also Powered lift. There are also real helicopters with more than one rotor like the CH-47_Chinook - see Tandem rotors for more. Friday (talk) 15:47, 26 October 2007 (UTC)

Actually it's from a videogame. Please don't make blank assumptions, it's a little condescending. Yep, those things certainly are real, but you didn't address my questions at all. 64.236.121.129 16:03, 26 October 2007 (UTC)

The "Banchee" (I assume that's the name based on the filename) seems to have a lot of fins and protrudey-bits, which seem to make stealth more difficult. Yes, you can coat them all with Radar absorbent material, but that goes for anything you would want to stealthify, so this design is no more or less stealthy in that regard. Plus, if this design's rotors are just to provide lift, while a jet engine provides forward thrust, that's going to cause a lot of intersting flight dynamics at any kind of high speed... Arakunem 15:55, 26 October 2007 (UTC)

Haha, the protrudey bits aren't relevant to the basic question I'm asking now are they? I'm talking about using two small turbofans to provide lift instead of a large main rotor. So your points about the stealth aren't very relevant. I'm not sure if adding a jet engine would be a good idea or not, so lets throw it out. The basic question I'm asking is, why don't we use the twin turbo lift fan design? 64.236.121.129 16:03, 26 October 2007 (UTC)

Well, you did say it would be more stealthy in your original post... just commenting on that bit too. :) Arakunem^Talk 17:14, 26 October 2007 (UTC)

Sure, it looks cool, but did you look closely at the design? It looks like the props in the "wings" are just holes punched in the wings, with the engines of the fans mounted inside the holes. Apart from obvious problems like fuel lines, it doesn't look like those props could provide much lift, nor are the wings very stable-looking for a very heavy-looking aircraft. If you fixed those problems, you'd probably end up with something looking quite like the V-22 Osprey. I also notice what appears to be an air intake at the front of the vehicle, so there might be a jet engine of some type hidden under the vehicle. -- JSBillings 16:37, 26 October 2007 (UTC)

I'm not sure what you mean by props. Do you mean propeller? There are none. Those are turbofans. Ignore the intake, I'm just talking about the twin turbofans. Hmm, a turbofan should provide lift. The F-35 uses a single small one for STOVL, and has been demonstrated to perform VTOL in testing. Still this is mostly speculation. I was hoping for an answer from an avionics engineer or similarly qualified person. 64.236.121.129 17:10, 26 October 2007 (UTC)

(I used to be a flight simulator designer - now I work in video games - so I'm qualified both ways!)

Your basic answer is "We do - it's called a V-22 Osprey". But you can't possibly say that just because this thing looks cool in a game that it's even feasible in reality. Game designers (of which I am now one) do whatever looks cool with no thought for practicality. That thing looks great as a video game prop - but as an actual, practical aircraft, it's horrible!

• No streamining - all sorts of pointless things to add drag and slow it down. Could they really not put some cheap plastic fairings around some of those knobbly-bits to smooth it off a bit?
• Those gigantic pods (missile launchers?) are ridiculously large for the rockets they deliver. Compare the size with the ones on a real aircraft Image:AH-64 dsc04578.jpg for example. Why do rocket launchers need cooling vanes on them? The rockets come out in a bazillionth of a second - there isn't time for the launcher to get hot.
• It's about as far from 'stealthy' as you could imagine - with all sorts of curved surfaces and bobbly bits that you can't 'stealthify' with any amount of radar absorbing paint. (Did you know: that one time someone didn't fully tighten up one of the screws on the underside of an F117 stealth fighter - and that 'bump' was enough to make the plane visible from ten times the normal range?)
• For some reason, they appear to have used rivets of the kind that would hold a WWI battleship together to construct things like the cockpit canopy and the missile pods. Howard Hughes invented the flush rivet in the 1930's...please use it!
• It's painted with lots of pretty red bits just to be sure that all of our enemies can spot even if they have no radar or somehow didn't hear the ungodly noise from those gigantic engines.
• It's in no way clear how the air from those gigantic drag-inducing ducts would get into the engines. If the engines need that much air, they must be consuming one hell of a lot of fuel. Since there is almost no place to put any fuel (eg, no wings), it's going to have a very short range...unless those air ducts really are a lot bigger than they need to be.
• Why is the tail rotor so goddam huge and how does the power get to it? With twin rotors, it scarcely needs a tail rotor at all.
• Pilot visibility downwards or rearwards would be almost non-existant because of the bulge under the canopy and those two gigantic engines - so this is not going to be easy to land in a vertical manner or use for ground-attack roles.
• With all that drag, and no obvious means of forward propulsion other than the vertical fans - it's going to be slow as all hell - so it's no good for air combat.

Superficially, it looks a bit like an AH-64 Apache - but with overly large everything! It might make a good Disney-land ride attraction - but it's not in any way a useful aircraft design!

SteveBaker 17:13, 26 October 2007 (UTC)

Haha, SteveBaker, you didn't address the turbofans at all! That was kind of the point of the question. I kind of wish I didn't choose that image, because everyone is getting hung up over the doodads it has, but ignoring my questions (one of your points, I even mention in my first post). I was only talking about its twin turbofan design. Also everyone mentioning the V22 is a major -_-;. The only thing it has in common is the fact that it uses two rotors that spin in opposite directions. I'm talking about an aircraft with two smaller turbofans on each side of the body. 64.236.121.129 17:39, 26 October 2007 (UTC)

It's probably worth noting that the wing-prop-things are absolutely not turbofans. While a turbofan is an engine, these are clearly just propellors (that is, no ducting whatsoever exists to send their airflow to a turbofan engine assembly -- they're aligned for vertical thrust and nothing else). Apart from that, I think Steve has covered the bases better than I'm likely to. — Lomn 17:31, 26 October 2007 (UTC)

Well whatever you call them. Although the official webpage on it, http://www.starcraft2.com/features/terran/banshee.xml calls them twin turbofans. I'm just going by what it calls them. 64.236.121.129 17:46, 26 October 2007 (UTC)

That's fine within the context of a game that doesn't have to rely on reality, but if you're going to ask "why don't we actually make/fly/use these?", then you've got to go by what things really are. Also, I noticed in hindsight that SteveBaker did address the "turbofans" -- he noted that there's no way they could force a reasonable amount of air in to the engines (there's your turbofan reference) given the ducting, orientation, and so forth. — Lomn 17:49, 26 October 2007 (UTC)

Haha, you're mad again. In all fairness, I wasn't sure what they were really called, I alluded to that in my first post. ^^. 64.236.121.129 17:57, 26 October 2007 (UTC)

But every time someone called them something else, you jumped in and said "no, no, no, they're turbofans!" Once again, I'm perplexed as to why you bother posing the question when you've already decided what the answer should be. — Lomn 18:00, 26 October 2007 (UTC)

(Incidentally, I am the avionics engineer you were hoping to hear from) — Lomn 18:03, 26 October 2007 (UTC)

Yea, but that was before you pointed out that they weren't. ^^ Oh good, but you haven't really addressed my questions other than pointing out that the fans aren't turbofans. Oh, and you said they were too small, but that's why there's two of them, and the aircraft is small. Also there's the issue with the F-35 using one. 64.236.121.129 18:09, 26 October 2007 (UTC)

...because Steve addressed them. In short, this aircraft does not exist because it is, top to bottom, a hideously impractical engineering liability. It has no redeeming qualities apart from "it looks cool!" -- though I'll grant that it looks cool. — Lomn 18:15, 26 October 2007 (UTC)

Backing up a bit (to a shorter indent), the reason we don't see two small enclosed props providing lift instead of a typical main rotor is -- they're too small. The V-22 has been linked quite a bit above, but it's quite illustrative of the concept. It's a twin-rotor side-by-side configuration and the props are absolutely massive. Additionally, you can't just run small blades faster because you start bumping into the sound barrier, and the associated turbulence is murder on propellors -- this is the primary reason that prop-powered aircraft hit a speed barrier in the mid 1940s. — Lomn 17:55, 26 October 2007 (UTC)

Yeah - exactly. I didn't address that comment because it was meaningless. A "Turbofan" is a kind of engine, not a kind of 'fan'. The "official webpage" doesn't matter a damn - some guy like me thought it sounded cool so he wrote "turbofan" - he could have written "dark-energy powered cyclowidget" for all it matters. You wanted to know how it could be in REALITY. The thing that you drive with that engine is the thing our OP is talking about - and those are "rotors". Which for some arcane reason have been enclosed in some kind of gigantic and heavy-looking donut-shaped fairing. The Osprey uses a pair of 'turboshaft' engines which are essentially turbofans that are designed to rotate a shaft rather than produce jet thrust. I don't really see how you're going to drive those rotors with jet thrust - so I presume your "turbofans" are really "turboshaft engines driving rotors"...which is precisely what an Osprey does...only it does it without the ugly, heavy, radar-reflecting and ultimately pointless fairings. Incidentally, the other aircraft that this fiction thing looks like - the AH64 helicopter - is also powered by a turboshaft engine. SteveBaker 17:56, 26 October 2007 (UTC)

Haha, calm down steve. You're mad. Yea I called it a turbofan, but I wasn't sure what it was. You should know what I was talking about though. I described it well enough, the fans on the sides. Duh. I'm not sure how well they would perform in providing lift, but I do know that the F-35 uses a similar device for STOVL and it can even perform VTOL. Also those fairings WOULD reduce the radar cross section in two ways. One, they are smaller than a main rotor, so that already reduces it. And two, the fairing would act similarly to the fairing on the tail rotor of the RAH-66 Comanche. 64.236.121.129 18:04, 26 October 2007 (UTC)

The F-35 can use such a fan, yes, but there are major caveats. First, it's also using thrust vectoring from its main engine. Second (and far more important), it's hideously inefficient. No aircraft can possibly maintain the fuel capacity to use such a device as its sole lift source and have any practical use whatsoever. Simply executing a VTOL (instead of an STOL) cuts the max takeoff weight of a Harrier by over a third (meaning effectively zero payload) and significantly reduces its range as well. — Lomn 18:12, 26 October 2007 (UTC)

Note: here's an excellent video showing the F-35 rotating its jet exhaust a full 90° for VTO purposes. I would expect, though I have no reference, that the bulk of VTO thrust is derived from this engine with the lift fan providing balance. — Lomn 18:26, 26 October 2007 (UTC)

Uhh, that video specifically states that the lift fan performs without incident. Hence, most of the lifting force, comes from it. Malamockq 00:42, 27 October 2007 (UTC)

That's not a valid "hence" statement. The lift fan works, yes. That's how the video states it. The lift fan is necessary for the VTO to work -- but nowhere in there does it say what the thrust balance from the fan versus the jet is. I'm banking on the jet's far superior power, using thrust vectoring to help counter its off-center location, to provide the bulk of the thrust. It's just a guess, but I consider it quite reasonable. — Lomn 06:33, 27 October 2007 (UTC)

You obviously didn't even bother to read the F-35 article. The lift fan was one of the main reasonsn why the F35 was chosen over the F32. Also use common sense. If it was the jet in the back that was the primary force in VTO, then you would have the jet with its ass up, and its nose planted into the ground without the aircraft getting very far off the ground. The jet assists in VTO yes, but it's anything but the primary force behind it. Malamockq 00:05, 28 October 2007 (UTC)

Actually, I did read the F-35 article -- and found no specifics regarding the lift fan at all. However, this source rather clearly suggests that it's a 50/50 split, give or take (remember, center of gravity is not the same as center of geometry). Of course, it's a moot point. Simply being able to lift with a fan says nothing about the relative merits of this method of propulsion. In short, the merit is: it's small enough to fit in a fighter. The associated problem is the oft-mentioned inefficiency. To take off with this requires a hefty reduction in payload, combat radius, or some combination thereof -- just to take off. God forbid you actually try to sustain lift and propulsion with a system like this. The rich variety of aeronautical experimentation, coupled with the complete lack of a system like this seeing even a trivial level of use, should provide the final nail in the coffin of the theory that Starcraft is a good source of aircraft designs. — Lomn 07:23, 28 October 2007 (UTC)

If it's a 50/50 split, then that means you were wrong anyway. Yes we know it consumes a lot of fuel, no one is saying it doesn't. I believe the point is, that it simply works. Malamockq 13:29, 28 October 2007 (UTC)

My understanding is that "the point" has always been "this design looks obviously superior; why aren't we using it?" — Lomn 15:22, 28 October 2007 (UTC)

(ec)The difference with the F35 is that the enclosed rotor for VTOL is not used to provide lift after it starts moving forward. So far, I'm still not sure how the Banchee is going to get its forward thrust. The difference with the Comanche's fairing is that it is vertical. That design is meant to scatter radar from ground sources, so the tail rotor appears as a sliver from the ground. From the side view in the air, the fairing does increase the radar cross-section. It's a tradeoff based on the Comanche's expected mission profile. Those Banchee fairings will increase cross-section from ground radar, and since they are angled with respect to the horizon, from the air as well. Arakunem^Talk 18:13, 26 October 2007 (UTC)

Also see the CH-47 Chinook. That's kind of like your Banchee turned sideways, so the concept of 2 rotors (or "fans") providing lift and steering has already been done. Arakunem^Talk 18:01, 26 October 2007 (UTC)

As a practical matter, lift will look something like (length of blade)²*(rate of rotation), while air resistance to rotation is closer to (length of blade)*(rate of rotation)². A larger rotor moving slower is more efficient, and hence better from a fuel consumption point of view. Dragons flight 18:08, 26 October 2007 (UTC)

That's true... I didn't know that. But since there's two, wouldn't it help with efficiency and power? There's more air resistance when you use one large rotor. 64.236.121.129 18:15, 26 October 2007 (UTC)

Apart from all the other problems, yes. But only apart from all the others -- namely, that the rotors are too small. You're exactly right in describing why heavy-lift helicopters have two rotors, though. — Lomn 18:26, 26 October 2007 (UTC)

So it wouldn't work on a heavy carbo chopper. But it could work on a light attack/scout aircraft. 64.236.121.129 18:38, 26 October 2007 (UTC)

Wouldn't it be less maneuverable than a single rotor choope? Beekone 19:13, 26 October 2007 (UTC)

Not at all. It would be more maneuverable because the rotors are smaller, and less cumbersome. 64.236.121.129 20:25, 26 October 2007 (UTC)

Wouldn't the extra mechanics needed to drive two rotors and control them and such-like add a great deal to the weight and therefore reduce its maneuverability? --80.229.152.246 20:51, 26 October 2007 (UTC)

The HUGE thing with radar stealthiness is that flat panels reflect the radar beam away in one narrow, focussed direction (like a laser hitting a mirror) which is astronomically unlikely to reflect it back into the radar's receiver. Hence you're pretty much invisible. A curved panel, on the other hand, spreads the narrow incoming radar beam out into a huge arc - so some part of the reflected signal inevitably hits the radar's receiver antenna and you're BUSTED. Radar absorbing paint and gold plated window glass help a little - but they aren't anywhere near enough without having a stealthy shape. That's why the F117 is made of flat panels with sharp angles everywhere. There isn't a curved panel anywhere on the aircraft - and as a result, it's super-stealthy. Now, look at the picture of this fictitious aircraft - there are curved panels all over the place...notably in those useless fairings. If you wanted to be stealthy (with that kind of design) you'd make the fairing octagonal or something - with hard corners. The Commanche is somewhat stealthy - and has lots of flat panels...but it's far from perfect.

I'm not sure that I buy your argument that two smaller rotors makes you more manouverable. The most manouverable helicopters on the planet are the ones with a single rotor. What matters here is your angular inertia. Having large amounts of weight far from the center of gravity of the aircraft is a really bad idea. (Remember the old thing about a spinning skater pulling his/her arms inwards to spin faster...same thing here - keep the weight in the middle to turn faster). Most helicopters have the engine, the 'main mast' the weaponry and the fuel tanks (which are the heaviest bits) as close to the center of the helicopter as possible - with a really lightweight tailplane and lightweight rotors. This fictional plane has two honking great huge engines and two MASSIVE weapons pods mounted far out to either side - and the most complicated, heavy-looking tail assembly I ever saw in my life! To add insult to injury, it's got those huge (and unnecessary) fairings around the rotors - adding lots of structural weight far out from the centerline of the plane. It's certainly going to have a huge moment of inertia compared to (say) the Apache. The Osprey has similar problems with big wings and those complicated gearbox things out where the propellor/rotors are - but it's not a super-manouverable plane either. So without knowing more data - I'd have to say that your fictional plane doesn't look at all manouverable to me. SteveBaker 21:01, 26 October 2007 (UTC)

The B2 Spirit has curved surfaces. So does the F-22 and the F-35. Also it's possible to put radar absorbent materials on a fairing, while it's impossible to put it on an exposed rotor. Malamockq 00:42, 27 October 2007 (UTC)

The operating environment matters, too, though. The aspects of a radar signature a B-2 has to minimize (from below and ahead) are quite different from that of a helicopter (from all sides), and the fighters (1) only aspire to be semi-stealthy (again, from particular aspects) and (2) are still fairly angular. Contrast the F-22 with, say, an F-16 for a good illustration. — Lomn 06:33, 27 October 2007 (UTC)

That has nothing to do with my argument. Steve made the point that flat panels are vital for stealth, but I pointed out examples, where they obviously aren't. In any case, even if he's right, there's nothing stopping a helicopter from having angular, flat panels as a stealthy design. His main point seemed to be that the fairings around the ducted fans were round, therefore they weren't stealthy. But how is an exposed main rotor more stealthy? While I'm at it, it seems he's wrong about Ducted fans being less maneuverable, when the article on ducted fans specifically states that they can be thrust vectored. This greatly aids in maneuverability. Oh, and it seems you were wrong about bashing the original poster for calling those props, turbo fans. Indeed, according to the article on ducted fans, if powered by a turbine, they ARE called turbofans. Malamockq 00:21, 28 October 2007 (UTC)

The B2 flies only a high altitudes and flies pretty much in level flight most of the time - so only the underside has to be flat. The F22 and F35 are really only mildly stealthy - compared to F117, they are hardly stealthy at all. Our OP said This design looks stealthier...and there is absolutely zero evidence for that point of view. The thing is full of disasterously non-stealthy geometry. Things called "corner reflectors" (where three panels meet at right angles like the inside of a cube) are spectacularly visible on radar - they stick out like bright beacons. The obsession the designer of this fictional plane had with cutting channels through the body panels and adding boxes and winglets definitely means that far from being stealthy - it'll stick out like a sore thumb on radar. We know that radar absorbant paint is black - this plane is silver and red...it's not painted with radar absorbent paint. Truly - it's hard to imagine anything that looks less stealthy. Our OP isn't using EVIDENCE to make statements about the probably performance of this thing - it's just wishful thinking - or getting overly immersed in the game. SteveBaker 03:10, 28 October 2007 (UTC)

Uhh, most of your argument are on things the OP said he wasn't referring to at all. Didn't you bother to read his posts? He was just referring to the ducted fans, not the rest of the aircraft. So really, you're arguing a Strawman here. Like I already said, there's nothing stopping a helicopter from having flat panels if they really are most stealthy as you dubiously claim. The RAH-66 Comanche uses stealth technology and, it uses flat panels. Btw, don't make claims about how stealthy the F22 and F35 are. Back up those claims with a source, otherwise you don't have an argument. Malamockq 13:25, 28 October 2007 (UTC)

"Semi-stealthy" is common knowledge among the aviation community, or by anyone with a basic understanding of how stealth works (see the notes about aspect angles above). Apart from that, I'm not sure what points you're trying to score here. Steve and I have addressed both the aircraft as a whole and individual components thereof (particularly the engineering uselessness of the ducted fans), but it's rather frustrating when objectors hop from point to point, ignoring all evidence against them but gleefully proclaiming "you were wrong" when any perceived fault is found. — Lomn 15:20, 28 October 2007 (UTC)

What does "semi stealthy" have to do with anything I said? I'm also giving your baffled bewilderment back to you. I never said ducted fans were practical. But your objections are flawed, mostly because a lot of them don't actually have anything to do with the ducted fans. If you are going to answer his question, stick to what he's asking about. Don't keep harping on design of the aircraft, when he's just talking about the ducted fan design. If you really are an avionics engineer, you should be smart enough to stick to the question, rather than getting hung up over irrelevant points. Malamockq 17:14, 28 October 2007 (UTC)

see the Bell X-22 with it's external ducted fans, seems to be the closest to the concept.—eric 03:46, 27 October 2007 (UTC)

The X-22 wasn't exactly a success - it only flew for a few months (first flew in March'66, and crashed in August of the same year) - and it was the only time ducted fans were tried. The immediate successor to the X-22 (the Bell XV-15) looks a lot like the Osprey - and every other tilt-rotor craft since then. The ducted fans were clearly no the X-22's strong point! SteveBaker 03:10, 28 October 2007 (UTC)

Did he claim it was a success? Stop arguing Strawmen. And no, it wasn't the only time ducted fans were used. There's also the Moller Skycar M400. Malamockq 13:25, 28 October 2007 (UTC)

Geez that one hasnt even flown yet in decades of development. I see a pattern as to why ducted fans are still relegated to video games. And no I'm not argung strawmen... you brought up the Moller. :) —Preceding unsigned comment added by Arakunem (talk • contribs) 15:35, 28 October 2007 (UTC)

No it has flown. Hovered at least, but I'm not sure what your point is. Steve said the X-22 was the only aircraft that used ducted fans. He was wrong. The Moller does too. And you are arguing a strawman by criticizing the performance of ducted fans or the Moller. I never either of them are practical. Malamockq 17:05, 28 October 2007 (UTC)

You can't hold up the Moller skycar as an example of a working aircraft. The X-22 did at least fly...the SkyCar merely hovers at low altitudes...there is a lot of difference! According to our article: "As of late 2002, MI's approximately 40 years' of development has resulted in a prototype Skycar capable of hovering about fifteen feet above the ground." - this is from the SEC complaint about the company. The ductwork around the propellors is said to be mainly a safety thing with some small performance improvements only at very low speeds. But the thing doesn't work - it has been shown hovering at 15 feet altitude (where it's still in "ground effect" and you only need half the amount of thrust) - that's more like a hovercraft than an aircraft. SteveBaker 14:43, 29 October 2007 (UTC)

Hehe you can't make an argument in a discussion and then accuse anyone who responds of strawman. But fine. Here's my final response on this topic, since nobody seems to want to believe the ones who have responded. A direct response to the OP's question, ignoring all the rest: Occam's Razor. We (humanity) have not used this design because any advantage that one piece might have is countered out by disadvantages in so many others, as Steve has pointed out regarding stealth and turning rates. Also, those advantages can usually be realized different ways that are easier and better. Once a ducted fan aircraft can do more than hover while attached to a crane, maybe we will look at that too. But in 100 years of aircraft design, there have been some pretty smart people designing aircraft and rotorcraft. They've tried some way-out concepts and designs. If the OP's design was viable, it would have been done. This is life, not a video game. Arakunem^Talk 18:10, 28 October 2007 (UTC)

tl;dr anyone?

Subsection 1.1: I have seen gravity guns used in lots of films and computer games. Can anyone tell me why we don't make them? After arguing your points I will nitpick and backtrack until all focus is lost and the question becomes a mockery of itself. Any comparisons you try to make I will ridicule and point out that in the totally made up object is not exactly the same as what you are refering to until you question my sources and I will then back down. Lanfear's Bane | t 10:23, 29 October 2007 (UTC)

Yes, indeed. The OP's original question has been clearly and comprehensively answered: If this thing were real, it would be described as a tiltrotor and we don't make aircraft like that because it has no advantages over existing designs.

However, this is not the answer the OP was hoping for ("Wow! Yeah - wouldn't that be cool! Modern aircraft designers are so lame!" might have worked!) - so (s)he started to argue about the answers we gave - which is unfortunate because there is enough expertise here to look at the design rationally and tear it to shreds. That was the cause of the little spiralling debates. The bottom line is the same though - just because you saw it looking cool and behaving nicely in a video game doesn't make it 'real'.

One of the cool things about being a video game designer (and that's what I do for a living) is that you can completely decouple what something looks like from how it performs - and you can make things perform in absolutely any way your imagination leads you - without any reference whatever to real-world science. It's unfortunate that people then take on those utterly unrealistic things and assume that they have some real-world significance. SteveBaker 14:43, 29 October 2007 (UTC)

Haha, wow. You guys are mad! *pats both of your heads* Don't take the internet so seriously kiddies. ^_^ 64.236.121.129 17:24, 29 October 2007 (UTC)

It is not important at all, but I'm curious as to why you removed my comment.[3] 69.95.50.15 18:07, 29 October 2007 (UTC)

plc

what is programming logic control —Preceding unsigned comment added by Londhe.sunil (talk • contribs) 15:51, 26 October 2007 (UTC)

We have an article on Programmable logic controller that is highly relevant. Friday (talk) 15:54, 26 October 2007 (UTC)

Or maybe you're talking about Control flow? -- JSBillings 16:33, 26 October 2007 (UTC)

PLC is primarily a method of controlling things electronically, usually industrial applications such as motors, heating systems, lifts etc but can also be used in consumer products such as washing machines or cars. PLC devices have superseded more primitive electromechanical control systems such as relay arrays and selectors.GaryReggae 19:19, 26 October 2007 (UTC)

Walkie talkies and radios

Why do walkie talkies have a short range compared to radios? Does it have anything to do with the wavelength or frequency of the electromagnetic waves involved? —Preceding unsigned comment added by 86.138.210.65 (talk) 18:53, 26 October 2007 (UTC)

What do you mean by "radios"? Commercial radio stations? "Ham" radio equipment? FRS radios? Citizens Band radios? In any case, the main difference is likely to be power, more than anything else. Both because high power would require heavier, bulkier equipment (and/or shorter battery life), and because having too much range means having more users talking on top of each other, interfering with each others' communications. -- Coneslayer 19:00, 26 October 2007 (UTC)

I more meant what determines the range? 86.138.210.65 19:04, 26 October 2007 (UTC)

Like I said, mostly the power. -- Coneslayer 19:16, 26 October 2007 (UTC)

There are strict regulations dictating the wavelength etc of walkie talkies to ensure that other communication systems (for example Emergency Services) are not interfered with. Power is exactly the thing that dictates the range, your local radio station will have a huge mast which is needed to transmit radio waves miles around while walkie talkies only have a very small aerial. This also ensures the waves don't travel too far. Ham radio is generally slightly more powerful and an antenna of some kind is usually required. You may wonder why mobile phones can operate over such large distances but they use microwaves rather than radio waves to communicate and microwaves can travel much further. GaryReggae 19:24, 26 October 2007 (UTC)

Thank you. Are there an unlimited number of frequencies? What has all this got to do with electromagnetic waves? Im lost. —Preceding unsigned comment added by 86.138.210.65 (talk) 19:46, 26 October 2007 (UTC)

No radio waves occupy a portion of the electromagnetic spectrum. The frequency can be anything between 3Hz and 300 GHz. This is a relatively large gap but the radio waves that you would listen to are generally between 30kHz to 30 MHz, depending on whether they are AM (longwave) or FM (VHF, shortwave). Amateur radio tends to be towards the shortwave end. Radio waves at higher frequencies includes the aforementioned microwaves and UHF tv signals. Radio waves are only one type of electromagnetic waves, light, X-rays and infra-red waves are all part of the electromagnetic spectrum. There is a limit to how many different frequencies you can squeeze into that bandwidth, you can't put channels too close together as they interfere with each other but the same frequency can be used for different things in different places where the waves are not going to intefere with each other. [4] has a good basic explanation of how radio waves work. GaryReggae 19:58, 26 October 2007 (UTC)

You can have radio waves all the way down to not-quite-zero Hertz. (Radio frequencies below a few tens of hertz are useful because they travel through water quite well - so they are used for communicating with submarines). But you can't push the frequency up indefinitely because when you get up high enough (and 300GHz is about it) you start getting infrared "light" instead of "radio" - although it's all really the same kind of thing (electromagnetic waves) - but the properties that make radio work the way it does get less and less useful as the frequency increases. So no, there isn't an infinite range - it's a finite portion of the electromagnetic spectrum. Electromagnetic waves themselves go up MUCH higher in frequency. At the highest frequencies we call them 'X-rays' and eventually, 'gamma rays'. There is also a limit at the high frequency end because as the frequency goes up, so the wavelength goes down. At the very highest frequencies, you start getting wavelengths as small as the planck length and at that point quantum effects start coming into play and it's doubtful you could produce higher frequency waves than that. SteveBaker 20:34, 26 October 2007 (UTC)

However, there are an infinite number of wavelengths within the bounded range. --Elliskev 20:39, 26 October 2007 (UTC)

Yes, but signals being transmitted on one wavelength will overlap and interfere with signals on adjacent wavelengths: the original meaning of the word bandwidth. --Carnildo 22:24, 26 October 2007 (UTC)

If you mean CB walkie-talkies, they are restricted to 4 watts AM, the same as non-walkie-talkie CB sets, because the purpose of citizens' band is short-range communication. That way, a person in Texas can talk on the same channel as a person in Pennsylvania and they won't interfere with each other. There is only so much room in the band allotted to CB. The power is held low for another reason, skip. Radio waves in that frequency range (27 Mhz) bounce off the ionosphere and can come back down thousands of miles from the transmitter, so it's better if they're faint to begin with. --Milkbreath 22:50, 26 October 2007 (UTC)

There are frequencies that you are legally allowed to emit with no limitations on power (but sidebands are not allowed so there are practical limits). 13.56 MHz is one frequency. The microwave oven frequency is another one (somewhere around 2.5GHz) IIRC. --DHeyward 06:58, 27 October 2007 (UTC)

While all the above may hold true the question was why the 11 meter band, that part of the spectrum allicated to cb radio, has such a short range. One aspect not noted is the role an antenna plays. With very little power a high gain antenna is often capable of world wide propagation; limited by many factors such as time of day and sun spots, all which affect the atmospheres. A walkie-talkies' antenna, has a negitive db rating. My point is that a 4 watt walkie talkie with its rubber duck antenna may have an effective radiationg power of less than a fraction of 1 watt while the same 4 watts radio with good coax and antenna system may have an effective radiation of 100 watts or more. The average ham radio has a power rating of 100watts ssb, 45 am. An am single transmitts the carrier wave and two side bands thus requiring more power to produce than a single side band. An antennas rating given in dbs is simply the antennas ablity to concentrate more of its power in a directional pattern.

A few questions on Birds

Reading the recent question about gulls has caused me to wonder why certain types of birds (Pigeons, Pheasants and Chickens all definitely do it) nod their heads up and down when they walk? Is there a physical reason for it or is it just a habit these birds have got into over the years?

Also, while I'm on the subject of our feathered friends, I was wondering about the intelligence of them. Some birds, for example parrots and budgies, appear fairly intelligent while others, such as pheasants seem very dopey. Is there a connection between the size of the bird's head compared to its body and its intelligence? Or are all birds equally intelligent (or stupid!)?

Finally, can birds taste or smell things? I know they usually have good eyesight and good hearing (I think).GaryReggae 19:47, 26 October 2007 (UTC)

Regarding your first question. Pigeons' 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 while it takes each step, a pigeon locks its head in position whilst moving its body beneath it. At the last possible moment, the pigeon thrusts its head forward to the next 'lock' position, which it holds for the next step. In this way the parallax effects are minimised. The combined action of the steps and "head locking" gives the characteristic nodding appearance. See here and here for in depth studies. Rockpocket 20:33, 26 October 2007 (UTC)

Regarding your third questions. Traditionally it we thought that birds had a poor sense of smell. However more recent studies seem to suggest it varies dramatically between species and some may have very keen olfactory systems. See here for an overview. Birds also have the ability to taste. It been noted that some species will peck the wings of butterflies to determine whether they taste toxic. If they do the bird will release them, if not they get gobbled up [5] However, in general birds possess relatively few taste buds, on the order of 100 (humans have roughly 9000). Parrots have the highest number (around 350). Rockpocket 20:48, 26 October 2007 (UTC)

Finally, with regards to your second question, see Bird intelligence and there references therein. Rockpocket 20:50, 26 October 2007 (UTC)

I'm personally curious as to whether birds such as pheasants, turkeys, chickens and pigeons are actually as 'stupid' as humans tend to believe, or whether it's simply a form of prejudice/erroneous extrapolation, based on these birds' tendencies to mill around (what would seem to us, aimlessly) in flocks and their general docile demeanour. If so - I've been guilty of it too. --Kurt Shaped Box 06:35, 27 October 2007 (UTC)

And gulls .... you forgot gulls ... how can you forget about gulls? Or are you trying to broaden your horizons?

Anyway, of course it's prejudice. People tend to assume that their way of doing things makes most sense. When we see people from another culture do things their way we often think that's stupid because that sort of behaviour doesn't fit in well in the framework in which they themselves work in. But the other culture has a different framework (set of way to do things), and within that framework what they do does make sense (or not - of course each culture has its stupid habits too). If that is even the case with other peoples, then how can people understand the framework that other animals operate in? DirkvdM 08:19, 27 October 2007 (UTC)

Gulls appear to be pretty smart birds, as it goes. Compare a gull to a pigeon, for example and it certainly *seems* that the gull has more in the way of resourcefulness, interest in social interaction with others of its kind and curiosity about its surroundings. --Kurt Shaped Box 18:50, 27 October 2007 (UTC)

A lot of domesticated fowl are pretty stupid, judging from my own personal experiences -- I don't know if the intelligence has been bred out of them, or the fact that they were raised in boring conditions. I'd expect wild fowl to at least appear more intelligent, because they have to deal with a harsher world. -- JSBillings 13:41, 27 October 2007 (UTC)

Is it true that turkeys believe that they are safe from predators, provided that they cannot see the predator themselves? In other words, if they see a fox (or whatever), they'll just hide their heads behind the nearest object? --Kurt Shaped Box 18:46, 27 October 2007 (UTC)

Wouldn't evolution deal with that pretty quickly? Btw, do foxes live in North America? If not, that would not be such a good example. DirkvdM 08:10, 29 October 2007 (UTC)

Good question. I *thought* that there were foxes in North America... --Kurt Shaped Box 20:16, 29 October 2007 (UTC)

New World vultures are known for having a particular good sense of smell. Pfly 07:47, 28 October 2007 (UTC)

Broken link

When I tried to ask a new question on this page a minute ago, it got added to the page about the letter C. Has somebody vandalised it? —Preceding unsigned comment added by GaryReggae (talk • contribs) 19:48, 26 October 2007 (UTC)

There was a problem in the header, which I believe has been fixed. However if you got a cached version of the page, this may explain why you still saw the problem even after it was fixed. Friday (talk) 20:19, 26 October 2007 (UTC)

Science Info

Hi all, Can anyone here provide me with some help, Im looking for interesting information about science, scientists, audios, videos, pictures, articles and etc. All I need is some useful links where I can find my need. Thanking you in advance. —Preceding unsigned comment added by 84.255.171.194 (talk) 22:04, 26 October 2007 (UTC)

Try Google.-- Flyguy649 ^talk 22:05, 26 October 2007 (UTC)

Try:

Category:Images by scientific discipline

Category:Scientists

Portal:Science

Commons Category:Science

Rockpocket 22:18, 26 October 2007 (UTC)

For scientific articles, try Google Scholar. Icek 03:05, 27 October 2007 (UTC)

gender ratios in a species

Are there any species of vertebrates for which the male-female ratio across the entire population is not close to 1:1? Sex ratio seems to be the only article on this topic, but it says pitifully little about non-humans.--M@rēino 22:55, 26 October 2007 (UTC)

Good question, this. Entire population sex ratios are impossible to measure, so scientists instead have to model them. They will often measure fetal, birth, litter or weaning sex ratios. A few interesting things have been found. Fetal sex ratios appear to slightly favor the sex that is larger in size (usually males). A 1988 study by Jaarsveld et al showed that spotted hyenas (unusual in that females are larger than males) had a 47% male fetal sex ratio, but a 55% male juvenile sex ratio. Thus birth ratios are skewed to adjust for the fact more of one sex will die during weaning. However, this doesn't really impact the overall population and the differences are not significanly different from 1:1 anyway.

More interesting, and pertinent, is the situation with certain types of lemming. Wood Lemmings produce about 3 times as many females as male offspring. This is due to an unusual genetic system where they have two different types of X chromosome, X^x and X^O. Any combination of XX is female and X^OY is male as one would expect, but X^xY is female. These unusual females are fertile but only produce X^x ova, which mean they only produce female offspring. Its not fully known the extent to which nature balances up the differences in the adult population, but sampling studies seem to suggest that males do make up as little as 25% of the population at equilibrium (Bengtsson 1977). Lemmings are strange creatures, though, and their populations tend to be cyclical. Its hypothesized that a high female sex ratio may suit this life cycle as a buffer against local mate competition and inbreeding during population low points. Rockpocket 23:59, 26 October 2007 (UTC)

Insects often have many more females than males. With ants, for example, the males are only for procreation and only appear for a short period of time. I don't know what the male/female ratio is at that time, but most of the time there aren't any males at all, so you'd have to average that out.

Btw, for mammals, wouldn't it also make more sense to have more females, for the purpose of procreation? Women carry a child for a long time, but there need only be a few males because their job is done quickly. All the genetic variation can be in the females. And they can take over the male roles by becoming stronger. So I'd like to turn the question upside down. Why is there usually a 1:1 ratio for males and females? DirkvdM 08:38, 27 October 2007 (UTC)

An answer to that can be found in evolutionary game theory: the actual rigorous analysis is somewhat complicated, but the upshot is that spending equal amounts of resources to produce offspring of either sex is an evolutionarily stable strategy: if the general population deviates from this equilibrium by favoring one sex, one can obtain higher reproductive success with less effort by producing more of the other. For species where the cost of successfully raising one offspring is roughly the same regardless of its sex, this translates to an approximately equal sex ratio. Of course, all this assumes that the genes that mainly determine the sex ratio are not sex-linked themselves: meiotic drive genes, as in Rockpocket's lemming example, can play merry hell with the whole thing, at least until some other gene evolves to counter them. —Ilmari Karonen (talk) 23:57, 27 October 2007 (UTC)

Good answer, Ilmari Karonen. Mechanistically, of course, its easy to understand why most mammalian sex ratio are around 1:1. Its because the male sex gametes typically determines the sex of the offspring. Since males are typically XY, there tends to be a 50/50 chance each sperm contains an X or Y chromosome and thus a 50/50 chance of producing offspring of either sex. To deviate from the ratio at equilibrium, you have to evolve a way of influencing this genetically (as the lemmings did) or else you influence the survival of one sex over the other. Rockpocket 01:02, 28 October 2007 (UTC)

The ratio of lions is roughly 1:1 too? --Wirbelwindヴィルヴェルヴィント (talk) 07:59, 28 October 2007 (UTC)

According to a study of hunted lions in the Selous Game Reserve, "the adult sex ratio (36–41% male) [is] ... similar to those of unhunted populations." [6] A study of lions in the Maasai Mara National Reserve found, "overall, their sex ratio was almost at parity and varied neither spatially nor seasonally. Sex ratio was even among subadults but skewed toward males and females among cubs and adults, respectively." [7] Thus it appears the variable pressures on lions during their lives adjusts for sex ratio. It would appear males are more likely to die as they increase in age (not surprising considering the pride system) so more of them are born to make up for it. However, when you add juveniles, sub-adults and adults together, the ratio is around 1:1. Rockpocket 19:45, 28 October 2007 (UTC)

Thanks, everyone! --M@rēino 13:04, 29 October 2007 (UTC)

As an apropos: In this study: [8] it is shown that zebrafish may produce 75% males if the water is polluted. Another example of environmentally induced sex ratios is found in turtles, where turtles hatch into males or females depending on the temperature the eggs were stored at. EverGreg 12:27, 1 November 2007 (UTC)

Members of the order crocodilia have no chomosomes, their gender is created by incubation temperature. Mac Davis (talk)

All living things have chromosomes. One assumes you mean that crocodiles have no sex chromosomes. —Tamfang (talk) 07:06, 22 May 2008 (UTC)

October 27

Crude oil production

Hello,

Can anyone tell me what has been the total world production of crude oil, in trillions of tonnes, over the period 1859 to 2007?

Many thanks, Carlyon —Preceding unsigned comment added by Carlyon (talk • contribs) 00:16, 27 October 2007 (UTC)

Thats a tough one. Using this dataset from OECD, the total world production of crude oil between 1971 to 2005 was 1.107827 trillion tonnes (trillion meaning a million million). This table provides data back to 1960 in million barrels a day. Beyond that all I can find is Image:Hubbert world 2004.png, from which you could try to source the raw data back to 1900. Rockpocket 01:02, 27 October 2007 (UTC)

Calcium Gluconate Chemical Structure

I'm having trouble putting together the chemical structure of calcium gluconate. I've tried using the BKchem molecular editor or similar programs to lay it out but i've completely forgotten how to do so. If this was all still fresh in my mind from my school years, I'd have no problem. Wikipedia shows a good bit of information about calcium gluconate, but in particular I need to see in diagram form the chemical structure of said supplement. Again, I've completely forgotten how to put these things together. [9] —Preceding unsigned comment added by 76.177.150.63 (talk) 00:39, 27 October 2007 (UTC)

It's a salt of gluconic acid. The rightmost hydrogen in the structure is to be removed (and a superscripted minus sign is to be written right of the rightmost oxygen) to get gluconate. Calcium gluconate is made up of 2 of these units and 1 Ca²⁺ ion, compare with calcium acetate (I think the picture in this article is of the kind you want to have). I don't know the real spatial arrangement of calcium and gluconate ions which can be determined using X-ray crystallography. Icek 03:00, 27 October 2007 (UTC)

Let me see if I've got this straight. From the gluconic acid you've shown, remove the rightmost H and replace it with a superscripted -? How would i illustrate 2 of these units correctly? The shown unit enclosed in parentheses (or whatever the correct term would be here)? Then followed with Ca²⁺? Is this the only possible way of illustrating Calcium Gluconate? thank you very much. —Preceding unsigned comment added by 76.177.150.63 (talk) 23:25, 27 October 2007 (UTC)

You could also draw 2 gluconate molecules and a Ca²⁺ between them (with the right molecule being a rotated version of the left one - the Ca²⁺ should be close to both O^-), similar to the picture in the Wikipedia article (which is a rendering of a space-filling 3d model - the green thing is the calcium ion). Icek 09:08, 28 October 2007 (UTC)

3 dB per octave?

Is there a way of getting a 3dB per octave boost or cut over a wide frequency range? —Preceding unsigned comment added by 88.109.17.174 (talk) 00:45, 27 October 2007 (UTC)

Yes but if it's the simple answer I think it is, I suspect this is a homework problem. Hint: Single poles and zeros create 3dB/octave changes in power. --DHeyward 07:03, 27 October 2007 (UTC)

Uh, no, first-order filters are 6dB per octave.

But yes, it’s certainly possible to design a filter that only changes by 3 dB per octave. Perhaps the easiest way to design such filter is to use a digital filter. Just do an Fast Fourier Transform, manipulate the spectrum to have the desired frequency response, and convert back to the time domain.

It'd be a lot more complicated to design if you have to do it as an analog filter, but it'd still be possible. It'd have to be a high-order filter, that combines an equal number or almost equal number of high-pass and low-pass first-order filters within one circuit. To see that it’s possible to design such an analog filter, you could always split the signal into an arbitrarily large number of bands using a bunch of band pass filters, amplify each band separately by an appropriate amount, and then join the signals together in one output. MrRedact 08:09, 27 October 2007 (UTC)

Actually, I thought of a much easier way to design such an analog filter. Just combine a first-order filter with an analog multiplier in a feedback circuit such that the multiplier is doing a square root. MrRedact 08:20, 27 October 2007 (UTC)

Oops, wait, I think DHeyward may have hit the nail on the head. Are you talking about 3dB voltage per octave, or 3dB power per octave? I assumed you meant voltage. If you meant power, then the answer is a trivial first-order low pass filter or high pass filter. MrRedact 10:06, 27 October 2007 (UTC)

It was 3 dB per octave in voltage i wanted (power is dead easy). —Preceding unsigned comment added by 88.111.67.141 (talk) 15:44, 27 October 2007 (UTC)

OK, then did you understand my idea for the analog version of the filter? The input of the whole filter would be the input of a first-order filter. The output of the first-order filter would go to the + input of an op amp. The output of the op amp, which is the output of the whole filter, would also go to both inputs of a four quadrant analog multiplier. The output of the multiplier would go to the – input of the op amp. You might need a resistor or two in there to tweak the gain or bias, but that’s the basic idea. MrRedact 20:39, 27 October 2007 (UTC)

Yes I understand: a 6dB/octave roll off, when square rooted will give a 3dB/oct roll off? This is one way i thought of, but I want it to work very fast, so the analog mult idea may not be capable of the speed. (the accuracy is not that important- 5% will do)

A mosfet has a square law relationship between voltage and current. You should be able to turn 6 dB/octave in input voltgage to 3db/octave in output current pretty easily. You can use it directly or in the feedback of an op amp. --DHeyward 21:34, 27 October 2007 (UTC)

This idea of using a mosfet (insted of an anlog mult) as the squaring element in MrR's topology is interesting. How would I setup a mosfet circuit to give me a true square of the input voltage (including the dc level)? Also could it be a JFET?

I just googled "mosfet square root circuit". here is one. The middle opamp has the mosfet in the feedback with the drain as the output. This is what I was thinking. JFETs are square law as well though they may require different biasing to stay in saturation. But now that I think about it, you may need square function to get you to "power" and then "power" is 3 db/Octave. --DHeyward 02:22, 28 October 2007 (UTC)

Interesting circuit, tho Im not keen on the necessary inversion and the active offsetting circuit. But thanks for finding it!

Doesn't "3dB per octave" just mean "a factor of 2 for each factor of 2"? I wonder why it isn't stated more simply as "1/f" or the like. —Tamfang 22:19, 29 October 2007 (UTC)

Whether that definition is right depends on what you mean by "a factor of 2". For a resistive load, the power is proportional to the square of the voltage. The OP wanted the output/input power ratio to change by a factor of 2 for each factor of 2 in frequency, which means the output/input voltage ratio is only changing by a factor of sqrt(2) for each factor of 2 in frequency. That's not as easy to do as to design a circuit such that the output/input voltage ratio changes by a factor of 2 for each factor of 2 in frequency. MrRedact 23:43, 29 October 2007 (UTC)

stop watch hardware

I want to know the harware of a stop watch(just stop watch) whose accuracy is 0.1 second. —Preceding unsigned comment added by Gangt (talk • contribs) 07:24, 27 October 2007 (UTC)

See stopwatch. The rate of a mechanical stopwatch is controlled by the balance wheel while an electronic stopwatch uses a crystal oscillator. --Justanother 19:14, 27 October 2007 (UTC)

Shock in AC and DC

Why do we get sucked in and pushed out while receiving shocks?..Is it due to ac and dc shock?..What is the shock difference in these two and which one is more fatal?.. —Preceding unsigned comment added by 122.164.49.85 (talk) 08:56, 27 October 2007 (UTC)

See Electric shock#Issues affecting lethality which discusses this. 84.64.123.72 11:33, 27 October 2007 (UTC)

The shock causes your muscles to contract. This can mean that your hand is immediately, and involuntarily pulled away from the cause of the shock - but if you have a grip around the live object then your grip may tighten and you'll be unable to let go no matter what. SteveBaker 02:44, 28 October 2007 (UTC)

German Weinstein: Potassium tartrate or Potassium bitartrate?

Hi, the German article de:Weinstein links to Potassium bitartrate aka cream of tartar etc. and vice versa. Dictionaries say so, too. (See also de:Wikipedia:Auskunft#Weinstein. But Potassium tartrate claims that that is the main ingredient of "Weinstein", though easily confused with the other. Can someone clear that up, please? T.a.k. 10:06, 27 October 2007 (UTC)

I'm not sure what is correct, but I would note that the information was added by an anonymous IP as that IP's only contribution [10]. Given that the information is not sourced, and contradicts other sources, I'm not sure that the info should be trusted. -- 16:45, 31 October 2007 (UTC)

Granular layer - cerebellum

Granular layer redirects to cerebellum. Why is this and is this correct? Lova Falk 10:32, 27 October 2007 (UTC)

Did you see the granular layer section? Here's a link with some other definitions. JMiall₰ 11:48, 27 October 2007 (UTC)

Granular layers also occur outside of the cerebellum (most notably, in the cerebral cortex), so this redirection is not really appropriate I think. EelkeSpaak 15:32, 27 October 2007 (UTC)

Cost of heat

A man lives in a place where the temperature is below freezing all year round. His house is heated with electricity, and he has an electric water heater. He keeps his house at a constant 20C, except for the "cold room", in which the thermostat is set at 5C. The water heater is located in an area where the temperature is 20C. He decides to move the water heater to the "cold room", to gain more living space. (This does not significantly change the distance from the water heater to where the hot water is used.) The man notices that the temperature in the "cold room" remains at 5C, even though the water heater feels warm. Would the total monthly electric bill change because of the move? GarthGarth 13:31, 27 October 2007 (UTC)Garth

If I understand the assumptions correctly, no. Electric heaters are 100% efficient in the sense that they produce one kWh of heat per kWh of electricity. Since (by assumption) nothing else changed in the move, the total power consumed by the water and space heaters must be the same as before, although it may be differently distributed between them. -- BenRG 14:19, 27 October 2007 (UTC)

I can't see how that can be right. The hot water is loosing heat by means of radiation and conduction the rate of both are affected by the temperature difference between the hot water and the room temperature. Conduction is proportional to temperature difference and radiation goes as the 4th power.Theresa Knott | The otter sank 14:38, 27 October 2007 (UTC)

The water heater will have to work a little more to keep the water hot, compared to the 20C room, since more heat is being lost to the colder room. At the same time, the heater in the house has to work less to keep the 5C room at 5C, so the house heater will use less energy. So the monthly energy bill is probably going to change. Whether its up or down depends on more specific info such as efficiencies, volume/area of the rooms, etc, and a bit of calculus. Arakunem^Talk 15:26, 27 October 2007 (UTC)

The water heater will use more electricity due to the greater temperature differential between the hot water and the room. However, the wasted heat from the water heater will contribute to the heating of the room. So the room's heaters will work a little less, and the water heater will work a little more. Probably won't see much change in electrical usage.

But for the room the water heater was moved from, the room heater will have to work a little bit more than it did previously since the water heater is no longer contributing any heat. --Bowlhover 01:22, 30 October 2007 (UTC)

Obviously, this assumes the rooms are heated year round, and moving the water heater doesn't change the temperature of any of the rooms, and the new plumbing doesn't snake outside, and so on...--Duk 17:08, 27 October 2007 (UTC)

No, no change at all. Forget the details. The temperatures stay the same, so the same amount of heat is generated. The only problem might be efficiency, but since heat is the ultimate energy waste product, but also the goal here, efficiency will be 100%, no matter what. So unless more or less warmth leaks out of the house, for example because the heater is moved to or from an outer wall, energy consumption will remain the same. DirkvdM 17:52, 27 October 2007 (UTC)

That assumes that none of the heat from the water heater (and the water in it) is lost to the room. Arakunem^Talk 23:03, 27 October 2007 (UTC)

Actually, it's the opposite. It assumes the water heater is just another heating element in the room. There are 3. One for the 20C rooms, one for the 5C room and the water heater. The temperature doesn't change in the rooms. The heating elements were just rearranged. The details of the percentage of heat from each element is not asked, just the overall heat. It doesn't change because there are no changes in the temperatures of the rooms. The sum of the heat is the same in each case so the energy added is the same. --DHeyward 06:46, 28 October 2007 (UTC)

If the electricity is being turned to heat in both cases, there will be no difference. If the water heater works that way, but the heater from the room moves heat in from outside, which is more likely the case, the less efficient water heater will be doing proportionally more of the heating, and the electricity bill will go up. — Daniel 20:18, 27 October 2007 (UTC)

Hang on, hang on, hang on.

If the water heater loses some heat to the room, we can think of it as being less than 100% efficient at heating water, but it is guaranteed to be 100% efficient at heating the water+room system.

If the other furnace is outside, and if it is less than 100% efficient, it might well lose some heat to the outside, which would then be lost forever.

So, paradoxically, if the other heater is outside, the less efficient the water heater is, the lower the overall electricity bill will be...

(The only exception would be the case where the grossly inefficient water heater in the "cold room" ended up heating it above the requisite 5°C.)

But on the other hand, if the other heater is inside, and if it's less than 100% efficient, any heat it loses is lost to the room, so hey presto, it's 100% efficient after all. —Steve Summit (talk) 23:17, 27 October 2007 (UTC)

And then there's how leaky the windows might be... *shifty* —Preceding unsigned comment added by Arakunem (talk • contribs) 23:23, 27 October 2007 (UTC)

Makes no difference. There has to be some heat loss to the outside, otherwise waste heat from the water heater would heat the "cold room" above 5°, and for that matter the rest of the house above 20°. Whether that loss to the outside is slight or extreme is immaterial to the rest of the problem. —Steve Summit (talk) 01:03, 28 October 2007 (UTC)

...wait a minute. Did we just do someone's homework for him? —Steve Summit (talk) 01:04, 28 October 2007 (UTC)

It's okay. I think after reading this they'll be more confused, and have to resort to thinking through what their textbook says...Skittle 15:07, 28 October 2007 (UTC)

Ah - a homework question. Ok, just draw a box with a arrows for energy_in and energy_out. Since all the temperatures and house insulation stay the same, energy_out stays the same, and therefore electricity_in must stay the same. Forget everything else! --Duk 16:25, 28 October 2007 (UTC)

I don't think a water heater can ever be 100% efficient. It's heating water in copper tank which is connected via nice metal pipes off into the outside world. Being metal, those pipes are going to conduct heat away out of the tank - and out of the room too. The answer to this question depends on the relative efficiency of the room heater and the water heater. If the water heater is more efficient then your bills should go down - if it's less efficient then they'll go up. SteveBaker 02:42, 28 October 2007 (UTC)

Not so. See my "paradoxically" argument above. It'd be very hard for an electric water heater to lose heat directly to the outside world, without heating some part of the house up first. (But similarly for a resistive electric space heater, located inside the house.) —Steve Summit (talk) 03:44, 28 October 2007 (UTC)

Yes but thats the point. The heater has been moved to a colder room, therefore is losing more heat faster than it was in the warmer room. Thus, the heater's heater will be running more frequently to keep the water at its desired temp. Thus more power is used by the water heater simply because it is running more often. The second consideration is then, that the heat lost from the heater to the room means the room's heater will not need to work as hard to keep that room at 5C, so it will use less energy. So the total house energy bill will change, but without more info you cant say for sure which way it will change, and by how much. Arakunem^Talk 15:16, 28 October 2007 (UTC)

Explain to me again why it will cost more (or less) to heat a room with waste heat from an electric water heater, versus with heat from an electric heater. —Steve Summit (talk) 16:40, 28 October 2007 (UTC)

Yes, you are quite correct! I was looking at the components and not the system as a whole. *Awards one pie* :) Arakunem^Talk 18:21, 28 October 2007 (UTC)

I don't see the location making any difference in energy use in the specified, somewhat atypical, conditions. The 5 degree room is already electrically heated, so any heat lost from the hot water heater from the insulated tank or the water pipes or even the electrical wiring to the air in the cold room will displace heat which would otherwise have been consumed by the heater in the cold room which maintained it 5 degrees warmer than the outside. The heat from the water heater which would otherwise have helped heat the warm rooms will be replaced by additional heat from the electric heaters there. Zero net effect. If it were a real world home, and the water heater were moved from living space to an unheated garage or unheated basement, the electric bill might go up, since most homes do not have a room thermostatically maintained five degrees warmer than a constant temperature outside. The devil is in the details. Edison 21:10, 28 October 2007 (UTC)

Yeah, but the assumption was that the temperature in the rooms is thermostatically maintained.

I said it 'forget the details', Duk said that energy in = energy out and Arakunem said to look at the system as a whole. Same idea, the wording just improved gradually. If the energy in the system (the house) remains the same and the energy going out of the system (heat leakage from the house as a whole) remains the same, then the energy going in is the same. And all that energy would be in the form of heat, since heat is the ultimate energy waste product. It would have to be a very stupid heater if it didn't convert all the energy into heat - what else would it convert it into? DirkvdM 08:59, 29 October 2007 (UTC)

Light?

I have to disagree with you on this problem. When the water heater is moved from the hot room to the cold room, the house heater will be on more often in the original room since it must work independently to maintain the temperature. Conversely, the house heater will be on less often in the new room since the water heater is providing part of the heat. The total amount of electricity used by the house heater remains constant.

However, the water heater must keep its water at a constant temperature. More energy will be consumed if the air temperature is 5 degrees than if it is 20 degrees, and the newly-located heater will therefore use more energy than it did before. The conclusion is that more electricity will be used after the water heater is moved. Is my reasoning correct? --Bowlhover 01:22, 30 October 2007 (UTC)

No because the energy that is "lost" by the heater goes in to the room. Since the 5C room doesn't rise in temperature, the heat provided by the water heater offsets the heat that was used to heat the room to 5C. This is a rate problem where the sum of the heat entering the house equals the sum of the heat leaving the house. The temperature is constant so the heat added is constant. Nothing you do with location of the heat sources will change it. This is a Guassian sphere-like problem where the net heat flux is zero. --DHeyward 05:05, 30 October 2007 (UTC)

Yes, this is what got me earlier. Note that the heaters were specified to all be electric. Meaning X watts of electricity goes right into heat. If you look at the house as a system, rather than rooms, then the net energy change for the system will be zero. Look at it like this: If you had one big heater providing X amount of heat, that would be the same as having 2 smaller heaters providing X/2 heat, yes? Or 3 smaller heaters at X/3... The heat lost from the water heater is just another heat source. If the heater loses 100 watts to the room, thats 100 watts less that the room heater needs to furnish. Net change = zero. Arakunem^Talk 14:40, 30 October 2007 (UTC)

Why is hot water better for washing dishes?

Why is it that hot water is better when washing dishes? Why does it seem to remove more dirt/grease/debris than cold? Is it purely from the thermal effect? or does the sometimes higher pressure of a hot water tap jet also have an effect? 84.64.123.72 13:38, 27 October 2007 (UTC)

The main factor is that things dissolve more readily in hot water. For instance, a cup hot water can hold more sugar than a cup of cold water. This takes care of the dirt that dissolves in water. Most of the dirt (like fat) does not dissolve in water, so we add detergent to the water so these dissolve a well. Finally, some amount of mechanical force is necessary to speed the process along, which is where the brush comes in. This also means that if the hot water has greater pressure (not sure if that's true) it may have a slight effect. 14:14, 27 October 2007 (UTC) —Preceding unsigned comment added by Risk one (talk • contribs)

In addition hot water softens fat and allows emulsification with a soap or detergent more rapidly than at lower temeratures. Hey, it also makes doing the dishes more comfortable Richard Avery 15:13, 27 October 2007 (UTC)

"also makes doing the dishes more comfortable" - depends on how hot the hot water is. --Psud 00:53, 28 October 2007 (UTC)

Softening/melting fats is the primary reason. The liquid fat is emulsified by the detergent, this would take a lot long if the fat was still solid. Shniken1 17:19, 27 October 2007 (UTC)

Anyone else here use boiling water to clean out their frying pans? You don't even need soap if the water is hot enough - just pour it in from the kettle, let the fat melt and float to the top, pour it out, wipe the pan out with a cloth. --Kurt Shaped Box 18:54, 27 October 2007 (UTC)

Yep, also doing that avoids getting the pan too clean or something, according to my mother. And who am I to question her wisdom? Then you rub a tiny amount of oil into the pan's surface before storing it. And Dirk, I think you could only wash up with cold water if a) you didn't eat or cook any of the more interesting things I eat or b) didn't mind a thin film of rancid fat/grease on everything and c) didn't need to get things washed quickly and d) didn't have to concern yourself with germs. Skittle 15:02, 28 October 2007 (UTC)

Now that we've changed the subject into dishwashing tips, I could add one my husband sometimes applies: boil water and washing powder in a pan. The inside of the pan has never been so clean before! Lova Falk 19:06, 27 October 2007 (UTC)

A very slight effect, if any. Several years ago I started using cold water and I didn't notice a difference. Mind you, I do the dishes in two goes. I first apply the dishwater (with just a little washing up liquid, a fraction of what people in the US use), let that soak for 10 minutes while I do some other household task and then finish it off with ease. Mind you, I do this on the counter, not in the sink, with the dishwater in one of the pans, and then I dip the brush in that. Works perfectly. And then I have a good excuse to clean the counter when I'm ready. Win-win-win. :) DirkvdM 18:06, 27 October 2007 (UTC)

A side effect of using very hot water (at least for the final rinse) is that your dishes and glasses dry faster, with fewer water spots. —Steve Summit (talk) 18:30, 27 October 2007 (UTC)

If the water is sufficiently hot, it will also kill some bacteria. This may not be very relevant at home, but it becomes important if you're, say, running a summer camp where keeping the dishwashing water hot enough can mean the difference between one kid with diarrhea and 30 kids with diarrhea (and one outhouse). The problem is that the water needs to be actually uncomfortably, if not quite scaldingly, hot (at least around 50°C / 120°F or so; see e.g. [11], keeping in mind that chemical sanitizers are rarely available under camp conditions). Merely lukewarm water just makes the bugs grow faster. —Ilmari Karonen (talk) 23:27, 27 October 2007 (UTC)

You all seem to forget to rinse properly. Cold dishwater will just as easily dissolve all fat if given enough time. A brush (before and after the soak) will help this process. After that, rinse with a lot of water. Assuming any food stuff is soluble in either water or fat, this will remove everything and the pan should be as clean as the water. Right? Just try it with a very greasy pan. It would be nice if someone who has a petri dish at hand would try this. Btw, there is no need to remove/kill all bacteria. Actually, the rise of allergies in the last few decades has shown that it is actually a very bad idea. And in a normal life you're exposed to all sorts of sources of bacteria, so why become all clinical here? DirkvdM 09:09, 29 October 2007 (UTC)

electron transfer

what makes an electrin to be transfered from an atom to the other(e.g metal to non metal )in ionic bonding? —Preceding unsigned comment added by 195.225.63.210 (talk) 14:06, 27 October 2007 (UTC)

Electron configurations of lithium and fluorine. Lithium has one electron in its outer shell, held rather loosely because the ionization energy is low. Fluorine carries 7 electrons in its outer shell. When one electron moves from lithium to fluorine, each ion acquires the noble gas configuration. The bonding energy from the electrostatic attraction of the two oppositely-charged ions has a large enough negative value that the overall bonded state energy is lower than the unbonded state

Systems of atoms like to be in the lowest possible energy state. When the electron moves from the metal to the non metal the total energy of the sytem goes down.

Another way of looking at it is thinking about the forces involved. Some atoms attract electrons more strongly than others. Metals tend to attract thier outer electrons less strongly than a non metal. See electronegativity for more detals. So although the electron is pupped towards the metal atom it is pulled more towards the non metal one and so hops over to it making an ionic bond Theresa Knott | The otter sank 14:29, 27 October 2007 (UTC)

After which they would each go on their own merry way, were it not that the metal is now positively charged and the non-metal positively charged, so they are attracted to each other. A bit like free sex - the exchange precedes the attraction. :) DirkvdM 18:12, 27 October 2007 (UTC)

plants

Why are some leaves spickey —Preceding unsigned comment added by 213.122.27.220 (talk) 18:22, 27 October 2007 (UTC)

A reason that comes quickly to mind is that the spiky leaves provide an adaptive advantage in protecting the plant against predation (being eaten) by animals. So, it basically acts as a self-defense mechanism in plants like holly for example. Azi Like a Fox 19:24, 27 October 2007 (UTC)

In other cases, and depending on how spiky you meant, water storage may also be a factor "Cacti have never lost their leaves completely; they have only reduced the size so that they reduce the surface area through which water can be lost by transpiration.". Our article on Leaves, specifically leaves#Adaptations, suggests that "A transformation into spines protects the plants" so my water storage comment may be a misnomer.--VectorPotential^Talk 12:33, 28 October 2007 (UTC)

What leaves are spiky? Be specific. Malamockq —Preceding comment was added at 17:17, 28 October 2007 (UTC)

The ventral posteromedial nucleus!

Here's another one of my detail questions!
On this picture the VPL borders the pulvinar, while the VPM is more in the middle. However, our own beloved Wikipedia has this picture, that puts the VPL in the middle and the VPM bordering the pulvinar. My guess is that the VPM should be in the middle (because it is called medial), and that the Wikipicture has got the VPM and the VPL mixed up.
Is my guess right or not? Lova Falk 18:53, 27 October 2007 (UTC)

Here is an actual brain section for Macaque showing the VPM medial to the VPL. This diagram also shows the VPM in a medial position. I don't think the Wikipedia diagram is meant to be very accurate....it smashes a 3D structure into a flat diagram. --JWSchmidt 04:36, 28 October 2007 (UTC)

Thank you! Lova Falk 13:48, 28 October 2007 (UTC)

Plant Absorbtion

I was wondering if plants could absorb anything besides water (ie milk, or perhaps coffee?). Would such liquids have a negative impact on plant growth or would their roots just absorb only the water part of the liquid? Thanks, Valens Impérial Császár 93 19:17, 27 October 2007 (UTC)

If a plant absorbed only water, it would die of malnutrition. Luckily for it, the water it's getting is generally dirty. Literally. I remember something about putting cellery in water dyed red with food coloring and watching the vain-like things that bring in the water turn red. — Daniel 19:51, 27 October 2007 (UTC)

You can do the same thing with flowers. Put a red rose's stem in water colored with blue ink, and you get a blue rose (according to my old biology textbook anyway). Most plants probably have a very narrow range of acidity that they can survive in. I know that mixing up used coffee grounds in soil for tomatoes helps them grow, but the caffeine in fresh coffee will kill them (so maybe decaf?). I expect that the fat content is important, which means that milk would be difficult. Most of this information (optimal acidity, hardness, etc) should be well documented for the soil, so it shouldn't be difficult to find a drink that suits a plant, or a plant that can grow in a given drink. risk 03:50, 28 October 2007 (UTC)

These are two different phenomena. Plants absorb the water and nutrients they need through their roots. When you cut the stem of a plant and immerse it in dye you are bypassing the roots, the liquid flows up through the plant by cappilary action. -- Diletante 20:48, 28 October 2007 (UTC)

How to kill Mad Cow prions?

I've heard that they're incredibly resiliant to heat, cold, UV light, pressure, chemicals and radiation. What's the best way of sterilizing something that's been contaminated with Mad Cow prions? —Preceding unsigned comment added by 84.71.69.70 (talk) 22:53, 27 October 2007 (UTC)

Our Prion#sterilization section suggets autoclaving at temperatures of 134 degrees Celsius for 18 minutes, which will pretty much denature any protein. If you want it utterly destroyed, incinerate it at even higher temperatures. If you're asking whether you can sterilize contaminated beef to an edible state, the answer is a flat no, as any method of destroying or deactivating the prion will destroy the beef. Someguy1221 22:59, 27 October 2007 (UTC)

A few years ago, I remember reading that heating contaminated medical instruments (to give an example) in concentrated sodium hydroxide or hydrofluoric acid at insanely high temperatures and pressures was the only sure-fire way of eradicating the infectious agents completely. I guess that technology has progressed somewhat since then. --Kurt Shaped Box 23:04, 27 October 2007 (UTC)

Minor point, but you can't kill a protein at all, it's not alive. If you denature a protein it can still, in most cases, be refolded under ideal conditions. See Protein denaturation, Protein folding, and of course Prion.--VectorPotential^Talk 12:26, 28 October 2007 (UTC)

Rather than temperature alone, please discuss the possibility of chemical neutralization of mad cow prions. Would bleach or diluted bleach neutralize prions? If someone fed the cat using one of the cereal bowls, and I want to make sure that prions which might have been in the "meat byproducts" part of the catfood do not remain on the dish when I eat my cereal from the same bowl sometime in the future, would a soak in bleach solution inactivate the prions? Would any other household chemical be more effective? Edison 21:01, 28 October 2007 (UTC)

You might find this paper and the references it contains useful. Of note:

"Conventional hospital disinfectants including ethylene oxide, propriolactone, hydrogen peroxide, iodophors, peracetic acid, chaotropes, and phenolics have little effect on prion infectivity.... In addition, prions are resistant to inactivation by UV irradiation, aldehyde fixation, boiling, standard gravity autoclaving at 121°C, and detergent solubilization."

As well,

"Currently recommended protocols for prion decontamination include either (i) >2% available chlorine of sodium hypochlorite for 2 h, (ii) 2 M NaOH for 1 h, or (iii) autoclaving at 134°C for 4.5 h. Each of these protocols has important limitations: sodium hypochlorite and NaOH are corrosive at the concentrations required to inactivate prions; NaOH did not inactivate CJD prions completely in some reports; and extended autoclaving at high temperature is deleterious to many materials. Currently, some high-risk surgical instruments are soaked in 2 N NaOH for 1 h, rinsed with water, and autoclaved at 134°C for 1 h, while many other such instruments are discarded."

The paper also presents a 'combined' protocol that employs an acidic SDS solution (1% sodium dodecyl sulfate plus 0.5% acetic acid) followed by 121°C that does seem to fully inactivate prions. Again, I urge you to read the full paper, and to look up the references it cites. TenOfAllTrades(talk) 21:26, 28 October 2007 (UTC)

As far as anyone knows, a human eating the meat will keep it from spreading. There's no proof humans can get infected from eating meat from a cow with mad cow disease. — Daniel 00:29, 29 October 2007 (UTC)

Just to inject a little realism....any idea how many people have contracted vCJD (human form of mad cow disease)? Only about 160, total, worldwide. Almost all of these lived in the UK during the mad cow epidemic. The number of cases annually, world wide, is quickly approaching zero. You know how many domesically born cattle have been found in the US with mad cow disease? 2!! [12]. In my opinion, this shouldn't be high on your list of worries. ike9898 21:12, 29 October 2007 (UTC)

When our research group needs to really and truly destroy protein residues we bake metal or glassware at 400 C for 2 hours in oxygen. This converts all the carbon to carbon dioxide. Of course, there are lots of other materials which also won't survive being steralized in this way, so its practical utility may be limited. Dragons flight 09:16, 30 October 2007 (UTC)

Dropping uncertainties

When dividing two numbers with uncertainties, the end result should have a greater uncertainty right? However, when I am doing the following:

• [(2.91 ± 0.01g) / (2.55 ± 0.01g)]

I end up with:

• 1.14 ± 0.008g

which is lower than the two original uncertainties I had. Could this be correct?

Thanks. Acceptable 23:15, 27 October 2007 (UTC)

When dividing two numbers with uncertainties, the end result should have a greater relative uncertainty, which your answer indeed does. However, I get 1.141 ± 0.006 for the answer. Did you make an arithmetic error? —Keenan Pepper 23:30, 27 October 2007 (UTC)

Ah yes, a greater relative uncertainty makes more sense. I did the calculation several times and I'm almost certain that 0.008 is correct. Much thanks. Acceptable 23:42, 27 October 2007 (UTC)

I actually get something a bit higher than 0.008:

Max value = 2.92/2.54 = 1.1496

Min value = 2.90/2.56 = 1.1328

Median value = (1.1496 + 1.1328)/2 = 1.1412 ± .0084. StuRat 18:50, 28 October 2007 (UTC)

But unfortunately Stu that is not how errors are calculated, although it seems logical. The errors in science are not upper and lower absolute bounds but probabilities basd on assumed normal distributions. Our page on error propagation gives the general formula for calculating errors. Under the specific examples you can see that for a ratio, the fractional errors combine in quadrature. I get 1.1412 +- 0.0068. Cyta 21:16, 28 October 2007 (UTC)

Which, if rounded to 2 decimal places (the error, that is), would give 1.1412 ± .007. -- JackofOz 00:14, 29 October 2007 (UTC)

How did you get 0.0068? The relative uncertainty of the numerator is 0.01 / 2.91 = 0.0034. The relative uncertainty of the denominator is 0.01 / 2.55 = 0.0039. So the relative uncertainty of the ratio should be sqrt(0.0034^2 + 0.0039^2) = 0.0052. The ratio is 1.141, so the absolute uncertainty should be 0.0052 * 1.141 = 0.0059, yielding 1.141 +/- 0.006. Right? —Keenan Pepper 22:06, 29 October 2007 (UTC)

the problem here is that the conventional nomenclature fro uncertainty (x±y) appears to be unambiguous, but actually is not.

You must explicitly define what you mean when you use the "x±y" Nomenclature. For example, if "(x±y)" means "x, with an assumption of a normal distribution with an SD of y" then "(x±y)/(z±w)" has a defined meaning. If "(x±y)" has a different meaning, then "(x±y)/(z±w)" has a different meaning. Note that you need to understand both the statistics of the numerator and the statistics of the denominator before you can have any confidence in the statistics of the result.-Arch dude 03:21, 29 October 2007 (UTC)

Excellent point, Arch dude. However, in the absence of any other statistical information it's reasonable to assume the variables are independent and normally distributed (or log normal, which is practically equivalent if the standard deviation is small compared to the value, as in this case). So adding the relative errors in quadrature is a good rule of thumb. —Keenan Pepper 22:06, 29 October 2007 (UTC)

October 28

Red Onion Skinn cells

In Biology class, we observed a piece of red onion skin under a 40X objective lens and probably a 10X eye piece. A drop of salt water was added to the skin under the microscope, the red part of the cell shrunk. Is the red part the vacuole or cytoplasm of the cell? Acceptable 01:46, 28 October 2007 (UTC)

Usually, plant dyes (and other secondary metabolites and end products) are stuffed into vacuoles by the plant cell. They would wreak havoc with usual plant metabolism taking place in the cytoplasm. --85.179.20.169 08:36, 28 October 2007 (UTC)

Fall question

I got to wondering why tree leaves aren't all the same shape. You would think there'd be an ideal leaf shape that all trees would have settled down to, but the variety is practically infinite. Are there evolutionary pressures on tree leaf shape by species, or is it accidental? In other words, are certain characteristics of an organism of no importance for suvival, and do these characteristics thus more or less reflect some underlying symmetry or other order that is merely a manifestation of their peculiar origins or mechanisms? I hope that made sense. --Milkbreath 02:23, 28 October 2007 (UTC)

Few (if any) things are accidental when it comes to evolution, although there is always some 'noise', to allow a species to find a new optimum when the environment changes. On a large scale you can look at the difference between pine needles and leaves. Pine needles allow trees to survive very cold climates, whereas regular leaves allow trees to get the maximum amount of photosynthesis in more temperate climates. I expect it works the same way for differences between leaves. The shape of the leaf is the ideal solution for the area where the tree lives in terms of getting the most sunlight, surviving the cold, the heat, and so on. If two trees live in the exact same area, they may have different survival strategies. One tree may get the optimal amount of nutrition from the location, whereas the other may reproduce faster, expand it's habitat faster, or be better at surviving changes in the environment. I'm not an evolutionary biologist, but I figure that's how it works. And there is always the possibility that everything else being equal, there are several optimal solutions, and two trees arrive at different ones. risk 03:41, 28 October 2007 (UTC)

As Risk says, there's lots of different things that a tree needs to deal with: snow, wind, sun, heat, cold, rain, storms. Some need leaves that shed snow, others need leaves that aren't destroyed by cyclones, others need leaves that won't loose too much water in dry weather. Lots of variables means lots of different leaf shapes make lots of different "ideals". What about two trees in the same forest? Well they may also grow in disparate areas, and they may survive or thrive in different situations differently. (oh, and it's spring here - all our imported trees are starting to sprout their myriad leaves in myriad shapes. All our local trees kept their leaves over winter, so we here think it's funny to call that season "fall") --Psud 09:07, 28 October 2007 (UTC)

Most of the factors which affect leaf growth have been mentioned, but let me add disease, insects, and animals which eat or damage leaves. Unless the animal provides some benefit to the plant, like spreading seeds for it, the plant will want to minimize leaf damage. Having many small leaves may help here, as large animals won't bother with small leaves, and the leaves can be easily dropped if they become diseased. Small leaves would also fare better in strong winds, but wouldn't do as much photosynthesis, due to all the gaps between the leaves for sunlight to pass through. StuRat 18:26, 28 October 2007 (UTC)

Leaves are a critical weapon the the war between the trees and the grasses. Grasses and trees try to poison each other, and deciduous trees try to kill grass by annually blanketing the grass with leaves. The leaf shape and size is of critical importance in the success of this strategy. it is deeply involved with the activities of herbivores, so the evolutionary response times will ensure a large range of leaf shapes and sizes. The suburban ecosystem with Maple trees andblue grass is profoundly unnatural-Arch dude 03:06, 29 October 2007 (UTC)

An additional thought is that it is a mistake to assume that everything about a plant (or other organism) has been determined by evolution. Natural selection will only affect those traits that change the survival rate of the species. Sometimes that differential survival critically hinges on leaf shape (needles in evergreen trees with longer winters, waxy, pointy-tipped leaves in plants with areas of high rainfall, etc), but sometimes it does not. For example, a maple leaf and an oak leaf are quite distinct to our eyes, but are probably not all that different in terms of practical survival rates for the individual plants and their offspring. Matt Deres 16:29, 29 October 2007 (UTC)

Butterflies and the fate of the universe

A flap of the wings of a butterfly in India will, given enough time, alter the course of a tornado in the US. Not to put too fine a point on it, but it will inevitably change everything about the world. Will it do the same for the universe? Sappysap 03:54, 28 October 2007 (UTC)

• The way I understand it, that's not actually true. Rather than being taken literally, I think that statement is supposed to be a refernce to the fact that the causes of something like a tornado are so complex that minute events (eg the butterfly) that might not otherwise be associated with the outcome are related. 68.18.209.108 04:42, 28 October 2007 (UTC)

The butterfly effect is a vey specific illustration of the fact that the Earth's atmosphere is a complex and interconnected system in which small changes are quickly magnified. So attempts at predicting weather patterns more than a few days ahead are doomed to failure because we cannot practically collect enough starting data with enough precision to produce accurate estimates. By extension, it has become a metaphor for any natural system that exhibits sensitive dependence on initial conditions. It does not mean that the flap of the butterfly's wings will change everything about the world. Although the butterfly's wings could (in theory) change the course of a torndao, we know of no physical mechanism by which they could (even in theory) cause an earthquake, significantly affect the path of an asteroid, or change the temperature of the Sun. A belief in mysterious and undiscovered mechanisms which intimately link every feature of the universe is more akin to astrology than to science. Gandalf61 07:28, 28 October 2007 (UTC)

Let's put it in perspective. Here's the closest thing to affecting the Universe. Our Indian butterfly flaps it's wings, that causes a tiny (but important in our chaotic weather system) change in the course of a storm in Sydney. A lightning strike happens in one place rather than another and sends a radio pulse out into space. That pulse of radio probably doesn't go very far into the universe, and on the few occasions where it does encounter something, it has practically no effect. Then you consider that the lightning probably would have happened anyway, just somewhere a little way away from where it did happen, and that lightning flash would have been effectively identical from even a fraction of a lightyear away (if it was even detectable at that distance) --Psud 08:58, 28 October 2007 (UTC)

Alternatively, that new lightning strike hits the person who would later have discovered a viable way to extract energy from fusion on a small scale, which would lead on to globe-spanning revolutions in virtually every field of engineering. The technology would've allowed the human race to construct interplanetary and eventually interstellar transportation, and ultimately lead to the colonisation of the galaxy. Which would have an observable effect from that distance. "For want of a nail" and all that. GeeJo ^(t)⁄_(c) • 11:02, 28 October 2007 (UTC)

I feel I should point out that one needs a very strange view of the world for this question to even make sense. In order to pin the tornado on the butterfly you have to suppose that the butterfly's action could have been otherwise, but that everything after that just snowballs according to deterministic (if chaotic) laws. Future choices by other butterflies would presumably dilute the long-term meteorological influence of this one butterfly to the point where it didn't matter whether it flapped its wings or not. The analogy does make mathematical sense as a statement about initial conditions of chaotic systems, but it doesn't make physical sense unless you subscribe to some form of last Thursdayism. -- BenRG 14:39, 28 October 2007 (UTC)

That's a switch—pinning something on a butterfly. --Milkbreath 15:27, 28 October 2007 (UTC)

The problem here lies in one misstated word in the question: A flap of the wings of a butterfly in India will, given enough time, alter the course of a tornado in the US. - not will but could (with a very low probability). There are a bazillion butterflies and a bazillion wing beats - and many, many other sources of atmospheric turbulance - any and all of which are having some effect. It is the net effect of all of them that causes unpredictability. So had that butterfly not flapped at that exact moment, then perhaps the tornado halfway around the world and a decade off in time might not have happened. It's definitely possible - in a chaotic system such as our atmosphere, there is infinite sensitivity to these kinds of events. But for any specific wing beat of any specific butterfly, the odds are truly astronomically small. As to whether the event could cause universe-wide changes - yes, sure. I like GeeJo explanation as to how this could come about. It's definitely possible for a butterfly wing flap to deeply affect something over the other side of the universe a very long time into the future. Again - it's very unlikely - but for sure it can happen. SteveBaker 16:34, 28 October 2007 (UTC)

There are limits to the extent of the effect of a butterfly’s actions. Some parts of the universe can’t possibly ever be affected by a flap of a butterfly’s wings. Due to the inflation of the universe, most of the universe is beyond what can ever be reached by a photon leaving our galaxy now. MrRedact 19:09, 28 October 2007 (UTC)

And, depending on how you look at all this, you can even say "very likely" instead of "very unlikely". In a chaotic system, anything can affect anything; everything affects everything. So the likelihood is very high that "event X" (whatever it is) is caused (in part) by some ridiculously distant cause that you can't even imagine. What's very unlikely, of course, is that event X was caused by a particular ridiculously distant alleged cause Y. —Steve Summit (talk) 16:51, 28 October 2007 (UTC)

The answer is YES. Here is a fun homework problem from graduate statistical mechanics. Imagine that you knew the initial position and velocity of every particle in the universe, except that you misplaced one electron 4 light years away by 1 cm. How long does it take before that simple error, by virtue of the electron's gravity, gives rise to sufficient chaos that you can no longer predict the position of gas particles in front of you? It's an extremely small error, but it is magnified by each of umpteen interactions between the gazillion particles in any given air parcel so that appreciable chaos sets in after only a few minutes (if my memory serves). So yes, that damned butterfly will introduce chaotic effects in sensitive systems throughout the rest of the observable universe. Dragons flight 09:43, 29 October 2007 (UTC)

How does that chaos set in before the electron's misplacement can propagate (at the speed of light) to the origin? You might mean that the area around the electron becomes chaotic, but then what's the "4 light years away" about? Or perhaps you mean that the electron's entire electromagnetic field is appropriate to its actual position (as opposed to it, at $t=0$, suddenly being magically shifted by that centimeter), but I have a hard time seeing how you could have that field interact with everything else and yet have the wrong idea about its source's location. It's an interesting question — with what shape and speed does the "wave" of chaos from a disturbance propagate? — but I'm not sure how to get a quantitative answer from what you've said. --Tardis 16:08, 29 October 2007 (UTC)

Technically, it's an error in the local, t=0 gravitational field corresponding to a 1 cm error in what the position of an electron at 4 light year's distance would have been at time t=-4 years. For simplicity, I wasn't describing the time delay. Dragons flight 18:58, 29 October 2007 (UTC)

Anyway, how come it's always tornadoes? I want a butterfly to flap its wings in India, and a beautiful long-legged nymphomaniac to make a wrong turn and end up in my living room. —Steve Summit (talk) 16:54, 28 October 2007 (UTC)

Well, the actions of a butterfly could cause a long-legged nymph to turn up, but that's another story... Laïka 20:24, 28 October 2007 (UTC)

If you find it comforting that the likelyhood of either nymph or nymphomaniac (that's someone who is really enthusiastic about immature insects - right?) turning up in your living room is influenced by such things - then I strongly recommend butterfly collecting. SteveBaker 22:00, 28 October 2007 (UTC)

I think astronomical systems are still chaotic, but not nearly as much as terrestrial ones. For example, if two meteors pass close by each other, a tiny difference in there original position will make a much larger difference in there final path. Unlike terrestrial systems, however, these are incredibly rare and it will take a huge amount of time for the gravitational effect of a change in the earth's weather patterns to make a noticeable difference. Also, the result of a butterfly effect is the difference between one thing that doesn't seem out of the ordinary and something else that also doesn't seem out of the ordinary. A butterfly flapping its wings will change the weather forever, but the climate will remain the same. — Daniel 23:12, 28 October 2007 (UTC)

The Butterfly effect is an example of Chaos theory. Some physical phenomena can affect "initial conditions" in ways that are unpredictable even in theory. It is possible to construct a sequence wherein the fate of the universe depends on the indertimanite state of a subatomic particle that affects, via a cascade of events, the movement of a butterfly's wing. In practice, this will not happen in this universe. -Arch dude 02:49, 29 October 2007 (UTC)

Tartaric Acid

Do you know the boiling point of Tartaric acid? The melting point is 168°C - 170°C, but I cannot find the boiling point. All of the information that I could find is on this page: http://en.wikipedia.org/wiki/Tartaric_acid Thank-you for your help. 203.113.233.115 07:31, 28 October 2007 (UTC)

This site (bottom of page) lists the boiling point at 275°C: [13]. However, many other sites don't list a BP because most of the acid will decompose before it reaches that temp. StuRat 18:14, 28 October 2007 (UTC)

definition of orthologous , paralogous, analogous,homologous

definition of orthologous , paralogous, analogous,homologous —Preceding unsigned comment added by Sujbhaskar (talk • contribs) 11:35, 28 October 2007 (UTC)

See wiktionary:orthologous, wiktionary:paralogous, wiktionary:analogous and wiktionary:homologous. Algebraist 12:18, 28 October 2007 (UTC)

And Homology (biology) at wikipedia. Algebraist 12:20, 28 October 2007 (UTC)

Mushrooms

Is a mushrooms considered a decomposer or what? —Preceding unsigned comment added by 209.244.30.199 (talk) 17:12, 28 October 2007 (UTC)

The mushroom itself is not a decomposer... the mushroom is only the spore-producing fruit-like part of a fungus. The fungus decomposes organic matter. Sancho 20:34, 28 October 2007 (UTC)

If I understand right, not all fungi are decomposers. A decomposer, according to that page, consumes dead organisms. Certainly a lot of mushroom type fungi grow on dead plants, logs, etc, but aren't there also a huge number of mushroom type fungi that are symbiotic with plants? I'm thinking of Mycorrhiza type relationships. My (admittedly vague) understanding is that most land plants depend upon mycorrhizal fungi for their very survival. When you see mushrooms growing near a tree, are they getting their food from some dead organism underground or are they symbiotic with the tree, each helping the other? My guess is quite often it is the latter. Pfly 02:01, 29 October 2007 (UTC)

From the respective articles: "Decomposers are organisms that consume dead organisms, and, in doing so, carry out the natural process of decomposition." and "Decomposition (or spoilage) refers to the reduction of the body of a formerly living organism into simpler forms of matter." We eat dead things and reduce them to simpler forms of matter so we can use them for our own bodies. So aren't we (and all living things) decomposers? Actually, doesn't dead nature do that too? I'll ask that in a new thread. DirkvdM 09:40, 29 October 2007 (UTC)

fibrous and synovial joints

Are there two types of joints between the radius and ulna? I was lead to believe they are joined by a fibrous joint. Another article tells me they have a synovial joint to allow supination and pronation. Can anyone clarify please? kramnahtal —Preceding unsigned comment added by Kramnahtal (talk • contribs) 19:07, 28 October 2007 (UTC)

Pinhole cameras

How does a pinhole camera project an image? I thought you needed a lens of mirror to focus light. I read pinhole camera but couldn't find the answer. 72.155.207.79 19:47, 28 October 2007 (UTC)

The pinhole itself acts as the lens. The second sentence of the article states this clearly: "An extremely small hole in a very thin material can focus light by confining all rays from a scene through a single point." I assume you mean "glass" instead of "mirror"; there is no mirror needed in any camera. --24.147.86.187 20:25, 28 October 2007 (UTC)

I understand that. I'm asking how air focusses light. And a curved mirror can focus light, and mirrors are most certainly used in cameras. 72.155.207.79 20:37, 28 October 2007 (UTC)

A mirror is not needed in cameras. Yes, you can set up Newtonian-telescope style lenses but that's hardly standard. Maybe you meant "lens or mirror" up above, I now see. --24.147.86.187 21:13, 28 October 2007 (UTC)

There is no real focusing of an image in a pinhole camera. It would work even in a vacuum. This is because, if you pretend for a moment that the pinhole is only large enough for one photon to make it through, each position on the film could only have been illuminated by light coming from a single direction through the pinhole. Thus, if you place an illuminated 2D picture on the outside of the pinhole camera, each position on the film corresponds to only one position on the picture outside. So inside the camera you get a nice, clear image of what's outside. Someguy1221 20:56, 28 October 2007 (UTC)

The air doesn't focus anything. The pinhole acts as a sort of collimator, if you will. Take a pinhole camera with the front off, and aim it at the calendar page for October. Consider a point on the back of the camera where the image will be. Let's locate the point about halfway between the center and a side at three o'clock. Now shrink your eye down to microscopic size and put it on that point facing the front of the camera. You will see the whole calendar page. Now put a front on the camera that has a round hole in the middle about an inch across. You'll only be able to see a few dates off to the other side. Put a front on with a smaller hole, and you'll see only one day. Make the hole very small, and the only light ray that will be hitting your eye will be coming from a tiny spot. The same goes for all the other microscopic eyes stuck to the back of the camera, but each will see a different spot on the calendar page. Voila! You've got an image, upside down and backwards. --Milkbreath 21:09, 28 October 2007 (UTC)

Do this for me (don't just think about doing it - actually DO it!). Take a piece of paper and draw on the left a stick-figure to be the subject of our photograph. On the right of the page, draw a vertical line representing the photographic negative inside the camera.

Now (without the pinhole) consider light rays coming from the subject onto the negative. Light is emitted pretty much equally in all directions from every part of the subject. So you can draw straight lines representing rays of light radiating out from our stick-figure's head and going out in all directions - lots of them hit the photographic negative - and they hit it all over it's surface. Similarly, you can draw rays radiating out from the stick figure's feet reaching any point on the negative. In fact, light from everywhere in the scene can reach every place on the negative - so all you get when you develop the plate is the average of all of the light from the whole scene hitting every point on the negative. A big white blur in fact.

OK - so let's add a pinhole "lens" to our camera. Start again with another diagram) - put the subject on the left and the negative on the right just as before - but this time, draw a vertical line down the middle of the paper with a tiny gap halfway up - this represents the front of the camera with a pinprick-sized hole in it.

Now, lets draw those lightrays coming from the stick-figure's head. They still shoot out in all directions - but most of them hit the line going down the middle of the page and are stopped. Only a few rays make it through the gap in the middle of that centerline (the 'pinhole') and onto the negative. Notice that rays from the top of the stick-figure only hit the bottom of the photographic plate over to the right of your diagram. Now do the same thing with rays from the stick figure's feet - notice that ones that go through the pinhole only hit the top of the photographic plate. Do this with rays of light from all over the stick figure and you find that each point on the original subject emits light in all directions - but the pinhole shuts all of it out except for a teeny tiny amount - so light from each point on the subject ends up at a different place on the negative. When you develop the plate - you get a nice, sharp image because the light isn't all mixed up like it was without the pinhole.

You can deduce some other things with this kind of simple diagram: If the pinhole is too big, lightrays from several close-by points on the subject can end up on the negative in the exact same place. This results in a blurry (but perhaps still recognisable) image. But if you make the pinhole too small, almost all of the light rays from the subject will hit the line down the middle of your piece of paper - hardly any make it through that teeny-tiny gap in the middle. This means that the image on the photographic plate is rather dim (because not much light hits each point)...so you need either a more sensitive film or a much longer exposure (which in turn results in a blurry image if anything in the scene is moving or the camera is shaking).

The point is that the pinhole forces all of the light in the scene to pass through a single point - and blocks all of the light that was heading off in the wrong direction. A more conventional lens focusses light through a single point (the 'focal point') - which has the same effect as the pinhole. The benefit of the lens is that it gathers light over a larger area - so you can get more light onto the film without ending up with a blurry picture. The bigger the lens, the better the quality. This is why cellphone cameras are so crap compared to big SLR cameras. Pinhole cameras do have one HUGE advantage though - they keep the image in focus no matter the distance of the subject from the camera - lenses can't do that. Everything in photography is about these kinds of trade-off.

SteveBaker 21:13, 28 October 2007 (UTC)

Incidentally, this is the same mechanism by which squinting your eyes sharpens an image—you're effectively forcing light through a smaller pinhole. TenOfAllTrades(talk) 21:30, 28 October 2007 (UTC)

There's an episode of Home Improvement in which Wilson has Mark fashion a pair of glasses out of a piece of paper with two pinholes in it. Sancho 22:31, 28 October 2007 (UTC)

Thank you very much for your clear and helpful comments, and sorry for the misunderstanding, 24.147.86.187; I did mean or. 72.155.207.79 22:33, 28 October 2007 (UTC)

Incidentally there was a BBC show called "Genius of Photography" on the other night (Uk), it made a camera obscura out of a room. They went in covered it till it was pitch-black and cut a small hole. Projected onto the wall upside-down (and reversed?) was the view from out of the window. It was very impressive - possibly available on You-tube or that bbc-download thing. ny156uk 23:18, 28 October 2007 (UTC)

The very first response to this question began, "The pinhole itself acts as the lens." That's wrong.

For convenience let's talk about a specific use of a lens or pinhole: the use where you have an object and you're projecting an image of it onto a wall. In order to make the image, you must arrange the rays of light in such a way that each point of the object corresponds to one point of the wall.

By making the light pass through a pinhole, you achieve exactly that correspondence by simple geometry: from each point on the object, there is a line of sight through the pinhole to exactly one point of the wall. That's all there is to it! If the pinhole is point O, then point A of the object corresponds to point A' on the wall were AOA' is a straight line. Point B of the object corresponds to B' on the wall, where BOB' is a straight line.

But the downside is, the whole image is formed from the few rays of light that happen to be pointed at the pinhole. That's okay if the object is very bright, like the Sun, but otherwise you need the wall to be in darkness (a camera obscura), and even so the image is not all that bright.

The purpose of using a lens is to overcome that downside. With a lens, instead of using the few rays of light that come off the object and aim at a little pinhole, we can use all the rays that come off the object and land anywhere on the lens. By choosing the correct lens and placing it correctly, we can arrange to have light paths like APA', AQA', ARA', where P, Q, R are different points on the lens. And similarly BPB', BQB', and BRB'. And so on for all the other points on the object and all the points on the lens. These paths are not all straight lines, but the lens is curved in such a way that the light follows them anyway. That's what focusing means -- this bringing back together of the rays AP, AQ, and AR to a single point A'. And you need a lens (or a curved mirror) to do it. It gives you a much brighter image, the total brightness corresponding to the area of the lens.

But with a pinhole, you don't need to focus in the first place. The pinhole sets up the correspondence between points on the object and points on the wall by geometry alone. It doens't act as a lens because in this setup there is no need to focus.

(In all this I am pretending that the size of the pinhole is negligible. In real life it can't be zero size, and this limits how sharp an image it can form. This is another advantage of a lens.)

--Anonymous, 10:00 UTC, October 29, 2007.

Esophageal Temperature Monitoring During Surgery

It is fairly common practice to monitor a patient's body temperature during a surgical procedure with the use of an esophageal stethoscope with a temperature wire inside of it. Does the temperature wire hook up to a machine that reads the data and then displays a readout? Or how does that work? Also, is it possible to lose the esophageal stethoscope in the esophagus? Thanks, Lilly Upstairs —Preceding unsigned comment added by 24.19.72.81 (talk) 22:03, 28 October 2007 (UTC)

Effective Projected Luminous Lens Area

This term is found in Federal Motor Vehicle Safety Standards for testing of lights for motor vehicles. I am trying to understand this term (EPLLA) in the context of a motorcycle turn light. I want to know how to measure this EPLLA and determine whether or not my turn lights are over the required 3.5 square inches required by the regulation. Can someone explain to me in somewhat laymen's terms what Effective Project Luminous Lens Area is and how to measure it? Thank-you 154.20.86.223 22:50, 28 October 2007 (UTC) Ray Kwan

Ray, EPLLA means the area of the effective light-emitting surface of a lamp, measured by determining the area of the 2-dimensional graphic representation of the lamp's lit lens area on a plane perpendicular to the lamp's reference axis and touching the most exterior point of the lens. "Reference axis" means the H–V axis used for photometric requirements, i.e., the effective centre of the lamp's beam pattern as produced at the lamp.

To simplify this and bring it into the realm of practical application outside of a compliance laboratory setting: The reference axis of most automotive and motorcycle lighting devices is reasonably easy to determine; it is "straight back" from the device with the device oriented in space exactly as it is oriented when installed on the vehicle. if you will place a sheet of fine-grid graph paper such that it forms a vertical plane at 90° to the lamp's reference axis, move the paper such that it just barely touches whatever part(s) of the lens protrude closest to the paper, illuminate the lamp, trace the blob(s) of light on the side of the paper opposite the lamp, and then calculate the area enclosed by your trace, you will have a close enough approximation of the device's EPLLA for most purposes. The thing you will have to be most careful of is accurately tracing the blob(s) of light. If your device uses multiple light sources, such as a cluster or array of LED emitters, you must trace each individual spot of light, omitting the dark areas in between, then total up the areas of each trace to arrive at your EPLLA.

It sounds like you've modified your motorcycle's directional indicator system in some fashion and are trying to determine if the modified or handmade indicators meet the EPLLA requirements. Good for you, most people don't bother, but be aware there are other safety performance requirements for vehicle lighting devices, as well. Intensity through various vertical and horizontal angles, intensity ratio between bright and dim modes of a park/turn or brake/tail lamp, etc.

For additional explanation, you may want to read this technical bulletin as well as this one and this one, keeping in mind that they primarily make reference to the 7¾ in² and 11⅝ in² EPLLA requirements for passenger car and large-vehicle brake lamps, respectively. Also, you may want to read through this NHTSA rulemaking discussion which goes into detail on the meaning, intent, and methods behind EPLLA requirements. If you wish to discuss vehicular lighting with more specificity, feel free to contact me via my talk page. --Scheinwerfermann 03:35, 29 October 2007 (UTC)

October 29

Batch experiment for denitrification endpoint in wastewater treatment

I am told the endpoint for denitrification in biological wastewater treatment can be determined by a batch experiment. What is the step-by-step procedure for conducting such an experiment and are there electronic sensing techniques for obtaining the same information in a continuous fashion? Thanks Thinkaboutlife 03:43, 29 October 2007 (UTC)

Gas formation at extreme low pressure and temperature

This question about wind at the miscellaneous desk spinned off into extreme planetary circumstances, with the planet so far from its star (if any) that it receives no heat (well, of course there is no absolute zero for anything). So I looked up the freezing point of helium, which is 1.15 K at 66 atm. Which would mean that even at extreme low temperatures, there would still be an atmosphere (however thin) of helium because of the vacuum surrounding it. But what about other gases? I guess I'm asking about the bottom left corner of the phase diagram (now why didn't I learn about that at school?), so extreme low pressures or a vacuum. But the article doesn't deal with that extreme. Let me start with one extreme:

• Would uranium be gaseous in outer space?
• And on above planet, at, say, an extremely low 1 Pa, what would be the boiling points of the various elements? The graph at the article doesn't go below 0.1 atm (= 10,000 Pa). And then at 10 Pa, 100 Pa, etc?

I suppose the atmosphere (which has no wind - the point of the original question) would be built up in layers consisting of the various elements with Helium sitting at the top. DirkvdM 07:18, 29 October 2007 (UTC)

On a phase diagram, you will notice that water is liquid at 1 atmosphere and room temperature. However, we also observe that water will evaporate from lakes and puddles. This is because even though the substance is naturally a liquid under those conditions, some fraction will spontaneously change into a gas through a process described by the vapor pressure. This is true for all substances. Uranium, like most metals, is naturally a solid in the limit of zero temperature and zero pressure. However, at all temperatures above 0, some small fraction of atoms will spontaneously turn into a gas and escape since there is zero ambient pressure. For most solids, the rate at which this occurs is neglible not only compared to human experience, but also compared to the age of the universe. In other words, the amount of time before satellites "boil" away in the vacuum of outer space is truly astronomically large. Dragons flight 11:52, 29 October 2007 (UTC)

Another way to think about that is that the concept of 'temperature' is really only a statistical average of the speeds of all of the molecules in the material. Even at fairly low temperatures, some molecules will be moving quite quickly (although the majority are not). Those few fast moving molecules may have enough kinetic energy to escape the surface no matter what. So all things with temperatures above absolute zero (which is to say: "all things" since absolute zero is unattainable) will lose molecules at some rate. But the statistics of the thing mean that the rate will be exceedingly slow at low temperatures because the probability of molecules having enough energy to escape becomes very low indeed. At higher temperatures that probability increases and evaporation will happen to a much greater degree - and finally, at the boiling point of the material, all of the molecules have enough kinetic energy to shake themselves loose and escape to form a gas. SteveBaker 14:06, 29 October 2007 (UTC)

Broad spectrum antibiotics

I know that Penicillin is a broad spectrum antibiotic, but was wondering if all antibiotics ending in cillin are broad spectrum. I couldn't find the answer here on Wikipedia or online, so thought I would ask here. Thanks. Jeffpw 08:52, 29 October 2007 (UTC)

Penicillin is not a broad spectrum antibiotic. It covers a relatively narrow spectrum of organisms, and is useless in Gram negative infections. In fact, most of the "-cillin" drugs were developed in order to find drugs with a broader spectrum than penicillin. You will find more details in the penicillin article, which lists narrow, moderate, and extended spectrum penicillins. - Nunh-huh 13:13, 29 October 2007 (UTC)

Drop dead on the Moon

If you'd drop a dead body on the Moon, what would happen to it? Would it decompose? DirkvdM 09:43, 29 October 2007 (UTC)

It depends on where you drop it on the moon. If you drop it in the dark side, it'll freeze and if you drop it on the sunny side, it will fried. 58.109.93.128 10:23, 29 October 2007 (UTC)

Hmmm .. I assume "dark side" means the far side of the Moon, i.e. the side facing away from Earth, which gets just as much sunlight (two weeks on, two weeks off) as the side facing Earth. I blame Pink Floyd. Anyway, a similar question has appeared on the RD in Nov 2004 here> There is also a response on Ask Yahoo here. General consensus seems to be that there would be some decomposition due to the presence of anaerobic bacteria, as well as dessication and slow weathering as a result of temperature changes. Gandalf61 10:39, 29 October 2007 (UTC)

Actually, on the album someone says "There's no dark side of the Moon, really." but then goes on to say "As a matter of fact, it's all dark.". Which is another bit of nonsense. DirkvdM 11:48, 29 October 2007 (UTC)

Not at all; it is dark. With an albedo of .12, it's only as bright as worn asphalt. We probably think of it as bright because there are no clouds or atmosphere to shade it from the direct sunlight. Matt Deres 16:40, 29 October 2007 (UTC)

The albedo of worn asphalt is only slightly lower than that of bare soil on Earth (fresh asphalt, on the other hand, has an albedo of just 0.04). But what I meant was is that half the Moon is lit by the Sun and therefore not dark. But SteveBaker gives yet another interpretation below. DirkvdM 09:11, 30 October 2007 (UTC)

Over eons, the top several meters of the lunar regolith are stirred up via the action of micrometeorites, through a process known as lunar gardening (wow, a red link). Since there is no appreciable atmosphere on the moon, even dust flecks the size of sand grains will leave tiny impact craters (since they are moving at several km/s). Over the very long term (i.e. many tens of millions of years) such micro impacts would ultimately grind the body down to nothingness. Dragons flight 10:50, 29 October 2007 (UTC)

Ok, looks like it's a race between the bacteria in the body, dessication and being bombarded to bits. I suppose the lunar gardening is the slowest process. How much will the bacteria consume before the body is dried out and the bacteria die too (or become dormant at best)? Also, which bacteria would do this? By far most bacteria in our bodies are benevolent, but would they start decomposing the body after it dies? DirkvdM 11:48, 29 October 2007 (UTC)

Oh boy, there are some confused answers here! Let's try to clarify things a bit...

• The term "dark side of the moon" refers to the side of the moon that is never seen from earth. In this context, the word "dark" is as in "Darkest Africa" - it means "unknown", not "lacking sunlight". The far side of the moon is just as sunny as the near side (and it's not even unknown anymore - we have lots of photographs of it). However, there are places in some craters on the moon that never see sunlight where things stay perpetually frozen. The length of a 'day' on the moon is what we'd call a "lunar month" - about four weeks.
• Since either freezing or baking to the point where it would kill bacteria would be unlikely to take more than a few hours (the temperature in the sunlight is enough to melt lead). I'm pretty sure that bacterial action is a non-problem in something as thermally conductive as a corpse.
• So unless this body is tucked away on the edge of one of those very steep-rimmed craters, it would alternately freeze for two weeks then cook for two weeks. I'd say that dessication/mummification would be the most immediate effect (that's what happens to bodies left on cold/dry mountaintops) - but it's hard to know for sure. There is no oxygen - so the body wouldn't combust in the heat - but it would drive out all of the water.
• As for being bombarded by meteors - that could happen eventually - but it would be a very improbable event. There are no more meteors (per square mile) hitting the moon than there are entering the earths atmosphere. The reason the earth isn't pockmarked like the moon is because the air burns up the smaller meteors and the craters created by the larger ones get eroded by wind & rain and subducted by continental drift - where on the moon they stay intact indefinitely. Look up into the sky on a dark night - how many meteor streaks do you see? Do you think one of them would hit you if it didn't burn up? Well, the odds are about the same on the moon...a little less actually because the earth's stronger gravity is going to pull them more towards the earth than the moon.

SteveBaker 13:52, 29 October 2007 (UTC)

• "... the temperature in the sunlight is enough to melt lead" - huh? This page says the moon gets up to 123°C, and our article says lead melts at 327°C. How would lead melt on the moon? --Sean 14:34, 29 October 2007 (UTC)

I was about to make the same point as TotoBaggins - sunlight on the Moon is definitely not hot enough to melt lead. Granted that 123^oC is still too hot for most bacteria to survive, but for hyperthermophiles such as Strain 121 it is just right. I agree that bacterial decay won't be a significant factor for our Moon corpse, but I don't think we can rule it out completely. Gandalf61 14:40, 29 October 2007 (UTC)

Well actually, without air - the temperature depends completely on the reflectivity/emissivity of the object (it's ability to shed heat by radiation) - the moon rock has an albedo of 0.12 - meaning that it only absorbs 12% of the incoming sunlight and reflects the rest away so the moon itself stays relatively cool. Darker objects will get a lot hotter. But I meant that figuratively rather than literally. I apologise, I should be more careful. SteveBaker 18:13, 29 October 2007 (UTC)

Steve, you've got albedo backwards in this paragraph. An albedo of 0.12 means that it reflects 12% of the light, so it absorbs the majority. -- Coneslayer 19:59, 29 October 2007 (UTC)

Steve, seriously, it's not an issue of "maybe it will be hit by micrometeorites", but a certainty. Objects below about 1 cm in size never get hot enough to leave visible streaks in the sky, but the population mass density of space debris peaks at about 100 microns, and the rate is about one micrometeorite impact per km^2 per second. The Earth aquires some 50,000 tons of space dust per year. And yes, as astronauts discovered, the entirety of the lunar surface is well-mixed to a depth of several meters by the action of meteorite impacts over tens and hundreds of millions of years. Dragons flight 15:32, 29 October 2007 (UTC)

Yeah over a very long period of time, the body will be bombarded to nothingness - but we're talking in the millions of years range. Let's examine your statistic of 50,000 tons of material arriving per year - it sure sounds like a lot - but only if you don't do the math. That 50,000 tons is spread more or less evenly over the 500 million square kilometers of the earth's surface. That means roughly one kilo per 10 million square meters. That number must be about the same for the moon - so if our corpse covers 1 square meter of the lunar surface, it's getting an average of one ten-thousandth of a gram per year of micrometeorite bombardment. Even at the speeds of micrometeors - that's hardly going to shred it to pieces anytime soon. Sure, it might get unlucky and get hit by a 10 kilo monster...but the odds are vanishingly small. SteveBaker 18:13, 29 October 2007 (UTC)

Using the rate of 1/km² or 1/1,000,000 m², and assuming a person's body has about 1 m² of exposed surface on the top side, it would still take, on average, a million seconds for a micrometeorite to hit. That's 11-12 days. So, to be completely destroyed by micrometeorites would take a long time. It would be a shriveled mummy long before that. Also, from how high was the body dropped ? If dropped from Moon orbit it would splatter into tiny pieces immediately, at least if it hit rock. Terminal lunar velocity into a deep pile of Moon dust might leave the body largely intact. StuRat 18:32, 29 October 2007 (UTC)

As there's no air resistance, there's no terminal velocity. I agree that dust would be a less destructive landing surface than rock, but my understanding from the Apollo missions is that the regolith is pretty firmly packed -- which would make the impact destructiveness thing almost entirely a function of initial height. — Lomn 22:04, 29 October 2007 (UTC)

The terminal velocity of a dropped object is still finite: it's equal to the escape velocity (for the Moon, 2380 meters per second). The only way to get something moving faster is to actively propel it. --Carnildo 23:44, 30 October 2007 (UTC)

That... seems unlikely (though I'd be interested to see a writeup on it, most TV stuff is written assuming an atmosphere). Apart from that -- initial conditions other than zero velocity, even without active propulsion, can easily lead to an impact at higher-than-escape-velocity speeds. Not that that's really either here or there.

The 'dropping' was meant in more of a figurative way. Btw, for a dead body, nothing can be considered terminal anymore. :) DirkvdM 09:11, 30 October 2007 (UTC)

Peak Coal

What is peak coal? 58.109.93.128 13:24, 29 October 2007 (UTC)

Peak coal is detailed in the article on Hubbert peak theory. Lanfear's Bane | t 13:32, 29 October 2007 (UTC)

Jehovah's Witnesses & Marriage

Do Jehovah's Witnesses believe and or support marriage to other religions. The reason I ask this question is I am not a Jehovah's Witness and am engaged to one and her father isn't in support at all of us. The rest of his children are married to a Jehovah's Witness. His brother isn't one and is married to one. Any help would be appreciated.

Thanks,

(email removed per instructions at top of page) —Preceding unsigned comment added by Timfreidag (talk • contribs) 14:47, 29 October 2007 (UTC)

• In most religions, getting the blessing of your fiancee's preacher, and then getting the preacher to perform the ceremony, is a sure-fire way to overcome this obstacle. Of course, you and your fiancee should be prepared for the possibility that the preacher is also intolerant of interfaith marriages. --M@rēino 16:33, 29 October 2007 (UTC)

Surely not! Surely religion is all about tolerance? If his brother is married to a JW, surely it would be possible for you? He may be using his faith as an excuse if he is not happy with his daughters choice of partner. (That's not that I am saying there is anything wrong with you, I am just hazarding a motive for his actions). Lanfear's Bane | t 16:54, 29 October 2007 (UTC)

You’d probably get much more knowledgeable answers if you moved this question to the Humanities reference desk, or perhaps the Miscellaneous reference desk. Indeed, I think the Science reference desk may be the worst of the reference desks to post this question to. As a general rule, the more that people are into science the less they’re into religion, and vice versa. MrRedact 18:36, 29 October 2007 (UTC)

The policy of Jehovah's Witnesses is to marry within the JW faith. Marrying someone outside JW may be enough to be dismembered. Graeme Bartlett 00:41, 30 October 2007 (UTC)

I think you mean "disfellowshipped" :-) --Trovatore 00:43, 30 October 2007 (UTC)

No, No, those folks can get real uppity, I think he was right..;-)) —Preceding unsigned comment added by 86.4.189.9 (talk) 08:56, 30 October 2007 (UTC)

Alcohol - on the verge of anaebriation!

If I have a few glasses of wine and start feeling light headed, what is happening in my brain to make me feel like that? Thanks. —Preceding unsigned comment added by 88.144.1.100 (talk) 16:04, 29 October 2007 (UTC)

We have an article specifically on the topic of Effects of alcohol on the body. Friday (talk) 16:05, 29 October 2007 (UTC)

Twin prop aircraft

after flicking through the "What is the name for this kind of aircraft, and why don't we make them?" post, I was thinking. Everyone dismissed the tail rotor on a transverse twin prop aircraft as pointless, but if you did have both props spinning in the same direction and a tail rotor to counteract any net rotation, would rotational manoeuvrability not dramatically increase with charge over the speed and hence thrust from the tail rotor, possibly allowing extremely sharp turns to be made, even at low speeds? ΦΙΛ Κ 16:28, 29 October 2007 (UTC)

The problem in most helicopters is that the tail rotor consumes continuous engine power for no useful purpose. On a twin rotor/propellor craft you can run the rotors in opposite directions to counteract the rotation and have more engine power to spare. You can still manouver by pushing more power to one rotor than the other. In the few (mostly Russian) helicopters that have Coaxial rotors that rotate in opposite directions, they can be shorter, more compact and turn faster than the usual kind. However, there are severe problems with these designs too: the additional complexity of the design, the problems of air turbulance between the blades as they pass each other adds vibration and there is a risk that in extreme situations one rotor might flex and hit the other. Having the two rotors spaced well apart helps that - and that's exactly what the CH-47 Chinook does. This solves most of the problems with coaxial rotors and gets rid of the tail rotor - but your back with a much bulkier design. Incidentally - one generally wants to place the two rotors fore-and-aft rather than left-and-right in order to keep a more streamlined fuselage - the exception being in tilt-rotor designs where obviously a fore/aft configuration wouldn't allow you to tilt the rotors forwards to become propellors for forward thrust. There was an experimental helicopter out there a few years ago that used a turboshaft engine to drive the main rotors and took the ject exhaust from the engine and sent that back to a vectored thrust nozzle in the tail that took the place of the tail rotor. This is a wonderful solution - but suffers from one lethal problem. If the engine fails, then your normal autorotational landing option is gone because in the absence of any tail-thrust, the helicopter would spin like a top. I don't know whether they ever solved that - but you don't see helicopters built like that - so I guess not. Then there is this thing: Piasecki 16H and Piasecki X-49 - which also doesn't seem to have taken the world by storm! SteveBaker 17:52, 29 October 2007 (UTC)

A few points..

1. I'd contest that moving power from one rotor to another in twin prop rotor wing aircraft would provide any significant turning force at all, as to provide a force comparable with that of cutting power to the tail rotors in a helicopter, you would have to stop one of the rotors, which isn't really a possibility, whereas with the tail arrangement I suggested, you could have twice the turning force experienced by cutting power to the tail rotor.
2. In the turboshaft exhaust arrangement you mentioned assuming the rotors and engine were not disengaged when power was lost, the turboshaft's compressors would surely continue to drive air through the tail pipe at a velocity which would allow the aircraft to remain stable, even if a hard turn was required by the pilot as well to further maintain stability.

ΦΙΛ Κ 22:23, 29 October 2007 (UTC)

1. Even assuming that holds, what happens if you have to turn the other way? You've got to mount an even bigger (and still completely unnecessary) tail rotor to counteract two main rotors working in concert. On the other hand, with a standard counter-rotating prop arrangement, all you have to do to generate yaw is vary the pitch of the blades. Same power to both rotors the whole time, and no power wasted on a tail rotor.
2. I don't get your point. If the engine fails, what's powering the compressors?

Anyway, I think it's fairly clear that twin-rotor craft have no need for a tail rotor. It's extra weight, complexity, and power loss for no operational gain. Even if it somehow improves maneuverability (a claim I doubt, and the utility of which I doubt -- more on that), twin-rotor craft tend to be heavy-lift craft where maneuverability is not a priority. Getting back to why the supposed extra maneuverability of a super tail rotor is useless -- think of a helicopter as a motorcycle and the tail rotor as the front wheel. When maneuverability matters for a helicopter in combat conditions, it's at high speeds. Helicopters, like motorcycles, make high-speed turns by banking, not by steering. A tail rotor doesn't even provide a meaningful assist, because while it may affect the direction the nose is pointed, it won't affect the helicopter's inertia. The ability to spin like a top is not a highly prized attribute of helicopters. — Lomn 02:30, 30 October 2007 (UTC)

To explain my second point, the moment of inertia of the blades, the same thing that would cause the craft to spin if power was lost.ΦΙΛ Κ 14:15, 30 October 2007 (UTC)

ΦΙΛΚ misunderstands how helicopters work. They don't "cut power" to the tail rotor in order to turn - they alter the collective pitch on the tail rotor blades. (That's how come they can turn both left AND right! :-) SteveBaker 03:37, 30 October 2007 (UTC)

True, I know very little of workings of a helicopter and was really just making assumptions. But just to say, using the mothod of tail rotor speed variance to steer, you could steer both ways, one way by slowing it down, the other by speeding it up.

You absolutely can, it's just that pitch variance is a far better solution. — Lomn 14:34, 30 October 2007 (UTC)

Theoretically - you might - but not in practice. The tailrotor is driven from a set of gears from the main rotor so that as the main engine throttles up and down, the tail rotor automatically maintains the correct amount of correcting torque. There is no way to speed it up...although I suppose you could slow it down with some kind of clutch mechanism - they don't do that in practice (at least not on any helicopter that I'm aware of). SteveBaker 17:02, 30 October 2007 (UTC)

So just to clarify, twin engine airplanes often do not have counterrotating props. The increase in efficiency is offset by the cheapness of the identical engines on each side (and on single engine models). --DHeyward 05:54, 30 October 2007 (UTC)

Yes - airplanes - because the orientation of the engines to the line of flight would induce roll - not yaw - and roll is easier to stabilise because you've got wings and ailerons and a large amount of rotational drag and a huge moment of inertia along the roll axis because of those big wings and the big heavy engines (not to mention fuel tanks) stuck way out from the centerline. Those things don't work anywhere near so well for the yaw induced by lift rotors in a helicopter or tiltwing. However, the effect of engine torque isn't negligable. Some single-engined aircraft were notable for being able to roll much more sharply in one direction than the other. I'm thinking of the Sopwith Camel as an example. It's Clerget rotary engine actually rotated with the propeller(!) and had a huge moment of inertia. The heavy spinning engine and the short-winged/lightweight biplane design enabled the aircraft to turn much more quickly to the right than to the left - a feature that experienced pilots used to their advantage. However, it killed a lot of novice pilots - so it was a mixed blessing at best! SteveBaker 12:10, 30 October 2007 (UTC)

It still is problem with most light twins with non-counterrotating propellers and that is what makes their safety record less than singles. It's said that it's safer to land a single with no engine than a twin with one because Vmc induces a roll higher than stall speed and with no warning. Some airplanes had Vmc close to stall speed and the asymmetric thrust meant that the airplane was never coordinated and one wing stalled earlier. Vmc + stall = rolling/flat spin close to the ground. Very bad day. —Preceding unsigned comment added by DHeyward (talk • contribs) 13:51, 30 October 2007 (UTC)

Eh? If one of your engines has stopped - it scarcely matters whether it was contrarotating or not! SteveBaker 16:58, 30 October 2007 (UTC)

Actually it matters quit a bit. P factor will induce a rolling moment on one side more than the other. It is why there is a different L/R Vmc in non-counterrotating engines. Minimum controllable airspeed depends on which engine goes out and it's killed a lot of pilots. --DHeyward 05:47, 31 October 2007 (UTC)

Barriers beyond a Planck Length

Even with a Grand Unified Theory uniting all the forces under an overarching Quantum Gravity (allowing us to observe phenomena beyond a Planck Time and beyond a Planck Length), will it be possible to directly study the nature of singularities such as those of a black hole or the infinitesimal "place" we all came from? If we can observe beyond a Planck Length but not all the way to a singularity, what is the next barrier? —Preceding unsigned comment added by Sappysap (talk • contribs) 17:34, 29 October 2007 (UTC)

Even with the GUT at our fingertips, observing beyond plank length or plank time will remain impossible. The present inability to do this is not a defficiency of modern physics, but a necessary consequence of quantum mechanics. And while we know that quantum mechanics and relativity disagree with one another, a meta theory to correct this issue will not change presently known laws of physics. This is precisely because we know why they disagree. Quantum generally assumes gravity to be irrelevant, while relativity generally assumes space to be smooth (ok, there are a few other technical details). These are very valid assumptions for short range and long range interactions, respectively, but neither holds at a singularity. So, don't let the thought enter your head that an inconsistency in modern physics will allow future alteration of the present laws true outside a singularity; they won't (we'll still be figuring out the consequences of those laws, but the laws pretty much stay the same). Now, you might be asking yourself what the point of figuring out singularities is if we can't actually peer inside of them. The answer is that even unobservable interactions can have very measurable macroscopic consequences. There are questions that can't really be answered by physics right now, such as whether a singularity can exist without an event horizon, or what actually happens to a particle that impacts a singularity (it might produce an observable event). Further, if we have an accurate model for what might happen within a singularity, we can develop an model of the big bang that goes further back in time, perhaps making predictions about early distributions of various particles that may have presently observable consequences. Someguy1221 18:33, 29 October 2007 (UTC)

Among theories that attempt to unite quantum mechanics and general relativity, and which are sufficiently well-developed to make some inference about singularities, most tend to eliminate the traditional notion of a singularity entirely and replace it with some sort of quantum fuzziness. For example, in string theory, the core of a black hole becomes something colloquially resembling a tangled ball of twine (no joke). Dragons flight 19:37, 29 October 2007 (UTC)

Remove Blood Stains

What is the most effective way to remove small amounts of human blood stains from clothes (in particular, white cotton) ... preferably with common household products ... and not something unlikely to be found in a home ...? Thanks. (Joseph A. Spadaro 19:13, 29 October 2007 (UTC))

90° water and washing powder in a washing machine will get rid of all the blood stains even on white. Keria 19:31, 29 October 2007 (UTC)

Yes, don’t use hot water! --S.dedalus 19:59, 29 October 2007 (UTC)

Yes, 90 Fahrenheit and not Celsius. Sam Blacketer 20:01, 29 October 2007 (UTC)

Hydrogen peroxide 3%, applied to the item when it's dry. Wait until it's stopped bubbling, then rinse it out. Repeat as necessary. Make sure you don't splash it around, and wash it off any skin that it touches -- it won't burn you quickly, but it will burn you if you insist. Also it may degrade the fabric somewhat. --Trovatore 20:15, 29 October 2007 (UTC)

Sard wonder soap rubbed on wet and then soaked works well. But not once it has been washed in Hot Water. Graeme Bartlett 00:45, 30 October 2007 (UTC)

Spit contains various enzymes. I don't know if any of those would help break down blood. But even if it is just the water in it that helps, it's something you've always got handy to remove a drop of blood right after it landed on the cloth. DirkvdM 09:30, 30 October 2007 (UTC)

I work in a hospital and regularly end up with blood on my uniform. Hydrogen peroxide works wonders. No visible traces left. I'm not sure what the reaction does on a chemical level (does it destroy forensic evidence?), but on a macroscopic level I've not found anything better for removing blood from clothing. 152.16.16.75 10:32, 30 October 2007 (UTC)

The hydrogen peroxide worked perfectly. Many thanks. (Joseph A. Spadaro 04:19, 31 October 2007 (UTC))

Why does blood do that?

Why does blood become hard to remove when heated? What is going on there that is different for other stains? Dragons flight 00:31, 30 October 2007 (UTC)

I imagine it has to do with the blood being composed of proteins. My best guess (dunno why exactly) is that the heat denatures the proteins which then bind with the clothing material and each other forming a interconnected "fabric-protein mass." With this explanation, I would guess other stains with proteins probably behave similarly but they aren't as noticeable because the proteins are clear. I wonder if the iron ion (which with the iron binding amino acids gives the blood the red color) has anything other than a passive role in the staining. Would be nice if someone with more knowledge could speak up on this issue. 71.226.56.79 04:47, 31 October 2007 (UTC)

How can we remove cooked on blood

How can blood stains that are fixed by hot water be removed? DOes peroxide work on these too? Graeme Bartlett 00:45, 30 October 2007 (UTC)

Kinetic Batteries

Would it be possible to put some kinetic powered batteries (like the ones in watches/torches) in an mp3 player, so as that it no longer had to be charged/required batteries? —Preceding unsigned comment added by 78.147.220.128 (talk) 20:18, 29 October 2007 (UTC)

Possible, yes, but probably not feasible. MP3 players have significantly higher power usage than wristwatches, and probably benefit less from natural motion. As for torches/flashlights, my (admittedly limited) experience with them has been that a large assembly is needed to generate power (much larger than a typical MP3 player) and that you're not getting much battery life out of a lot of very intentional shaking. — Lomn 21:17, 29 October 2007 (UTC)

The power draw for my particular mp3 player seems to be about 40 milliwatts. (A single NiMH AAA battery will run the device for about 30 hours.) Note that the power consumption will be higher for a device based around a hard drive rather than flash memory. For reference, this document from the MIT Media Laboratory notes that the typical output from a self-winding watch mechanism is on the order of 10 microwatts, but that up to about 1 milliwatt can be generated if the arm bearing the watch is vigorously shaken. In other words, the design would have to be scaled up substantially to operate a music player. That document does discuss other ways to extract energy from human body motion, however. TenOfAllTrades(talk) 21:58, 29 October 2007 (UTC)

Still 33 milliamp isn't that much. I wonder if a little dynamo could be used. Surely those shake torches use more than 40 milliwatts. Some of them have 10 milliamp 5 volts over each of 9 or more diodes!--Dacium 03:43, 30 October 2007 (UTC)

Sure; some other options are discussed in the article that I linked. TenOfAllTrades(talk) 03:56, 30 October 2007 (UTC)

Surely the OLPC XO-1 laptop is an existence proof that a kinetic power source can work for an MP3 player; if you can crank a laptop computer to operate it, you could certainly crank the far-lower-power MP3 player to operate it.

Atlant 11:53, 30 October 2007 (UTC)

Yes - but there is a VAST difference between vigerously cranking a geared generator and just kinda picking up random motion from your body (which is what a self-winding watch does). The OLPC needs to be cranked fairly hard for five or ten minutes in order to give you an hour's worth of computing. An MP3 player would certainly need a lot less than that - but (as has already been conclusively shown) that's still a lot more than you get from incidental motion. SteveBaker 17:48, 30 October 2007 (UTC)

Certainly. I think the limitation here is one of marketability. It seems to me that it'd be hard to sell a CrankPod that is three times the size/weight of its competitors. I started to say "but doesn't need batteries" or "but doesn't need charging", but that's not really true. You've still got a battery (with any of these solutions), and you've still got to charge it -- you're just changing the charge method from a plug to a crank. — Lomn 14:32, 30 October 2007 (UTC)

Vacuum Sealers - for commercial use

There doesn't seem to be much information on Vacuum packing, I'm trying to vacuum pack food for PACKAGING purposes, i.e. to post or transport to places, and when I try my useless home vacuum packer the food just doesn't last when I *know* that it should. The food's outright growing mould after 2 days. I have a sneaking suspicion that the vacuum doesn't hold and that the uesless vacuum bags actually breathe air (permeability) and I need to invest in one of those $4000 ones that will do the job properly! Anybody aware? Rfwoolf 20:33, 29 October 2007 (UTC)

Even if you remove all the air there are still anaerobic bacteria and yeasts that will decompose your food. There is probably some oxygen left after you suck out the air, a domestic vacuum cleaner cannot create a very low pressure. And there would still be oxygen dissolved if the product was exposed to air, or had pores. Vacuum packaging will still have to sterilise the food by some means, or have some otherway to stop unwanted growths. Graeme Bartlett 00:50, 30 October 2007 (UTC)

The article on Tetra Pak might be interesting to you. --Mdwyer 15:26, 30 October 2007 (UTC)

October 30

Protein domain

Two different protein domains can have a same function why or why not?

If I consider two amino acid sequences of a protein with same domains but changes in 2 or 4 amino acids in the chains. Could it have the same function?

Respected teacher

My problem is that I considered 2 chains of the same protein

Chain A ---> n l i i l a n n s l s s " n g n v" t e s g c k e c e e l e e k n i k e f l q s f v h i v q m f i n " t s "

Chain B ---> n l i i l a n n s l s s " n g n " v t e s g c k e c e e l e e k n i k e f l q s f v h i v q m f i n t s

Those in double Inverted commas are excluded from the domain chain but they are considered in the same domain why? —Preceding unsigned comment added by Biomedicalpersonal (talk • contribs) 05:12, 30 October 2007 (UTC)

I do not understand what you are trying to ask in the second part of your question but I may be able to help you with the first part. A few amino acid changes in non-critical regions or mutations resulting in similar amino acids (see Neutral mutation) in critical regions may not cause measurable effect on the functioning or the interactions of the protein domain. It would help if you clarify the second part of your question about protein chains. By the way, these appear to be homework questions. The users on the reference desk are not supposed answer your homework questions, but if you have do not understand a concept or need help getting pointed in the right direction by all means ask away. 71.226.56.79 04:22, 31 October 2007 (UTC)

food poisoning ???

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

This question was removed for a reason. We cannot offer medical advice on either poisoning or allergies. If you are worried about the state of your friends health you should consult a medical professional immediately, especially if you believe she has been poisoned. Discussing it on the internet first should not be your immediate priority. Lanfear's Bane | t 21:41, 30 October 2007 (UTC)

production of particles by pair production method .

in the wikipedia article "pair production" only example of electron-positrion pair production is given . is it possible to produce particles like proton , neutron and neutrino by pair production method ? —Preceding unsigned comment added by Shamiul (talk • contribs) 12:30, 30 October 2007 (UTC)

Neutrinos and antineutrinos can be produced from a photon.[14] Like electron-positron pair production needing other particles involved in order to conserve energy and momentum, neutrino-antineutrino production from a photon needs other particles involved in order to conserve spin, which is a form of angular momentum.

Protons and neutrons aren’t elementary particles, but instead bound states of quarks. So in quantum chromodynamics, low-order particle interactions would include pair production of quarks, not of protons or neutrons. A quark and its antiquark can be produced from a gluon.[15] MrRedact 21:02, 30 October 2007 (UTC)

While these predictions from theory are very likely correct, we are currently far from being able to experimentally confirm pair production of neutrinos (because our neutrino detectors are not very sensitive). Icek 01:08, 31 October 2007 (UTC)

Anomalous hair

REMOVED. —Preceding unsigned comment added by 193.188.46.61 (talk) 13:23, 30 October 2007 (UTC)

(EC) Do not request regulated professional advice. If you want to ask advice that "offline" would only be given by a member of a licensed and regulated profession (medical, legal, veterinary, etc.), do not ask it here. Any such questions may be removed. See Wikipedia:Medical disclaimer and/or Wikipedia:Legal disclaimer. Ask a doctor, dentist, veterinarian or lawyer instead. Sorry, even a query that sounds innocuous should be addressed to a professional. Lanfear's Bane | t 13:32, 30 October 2007 (UTC)

REMOVED. --JWSchmidt 14:55, 30 October 2007 (UTC)

The original question did not ask for medical advice. My original comment made this point. There was no reason to delete my original comment. --JWSchmidt 18:23, 30 October 2007 (UTC)

REMOVED. --M@rēino 15:03, 30 October 2007 (UTC)

Per Lanfear's Bane's comment, we cannot offer medical advice. In this case, the original poster was seeking a diagnosis--the identification of the cause of a particular symptom. If someone would like to discuss in more detail why this constitutes a request for medical advice, please bring it to the Ref Desk talk page: WT:RD. [hidden unsigned comment by User:TenOfAllTrades made public for clarity]

I am appalled at this continuing deletionism by people who are apparently incapable of telling the difference between a request for an explanation of a biological phenomenon and a request for medical advice. To take this behaviour to its logical conclusion would result in the prohibition of any question relating to human biology (or animal biology for that matter). What causes blue eyes? What causes grey hair? Why does alcohol abuse cause liver damage? All are questions relating to biological phenomena - just as is "What causes an observed variation in human body hair types in humans?" Hiding comments about the removal of questions is also profoundly unhelpful. DuncanHill 15:20, 30 October 2007 (UTC)

One clear sign of a question that we aren't allowed to answer is one that starts off "I have some symptom..." or "A friend has some symptom...". This is quite clearly one of those - and we aren't allowed to answer it - period. The questions you put up as strawmen are not the problem here. I would like to turn this around and ask DuncanHill: "What kinds of question do you think the ban on giving medical advice is intended to cover?" - clearly it covers something or it wouldn't be there. What? Give me some examples. SteveBaker 16:38, 30 October 2007 (UTC)

Why don't we stop wasting energy here now and instead just send the questioner to where he asked the same question a week ago (8 times in fact). DMacks 15:16, 30 October 2007 (UTC)

Hey, can everyone confine metadiscussion to the talk page of the Ref Desk? This sort of debate about what questions are appropriate doesn't belong out on the Desk itself. TenOfAllTrades(talk) 16:52, 30 October 2007 (UTC)

• "can everyone confine metadiscussion to the talk page" <-- If content is removed from this page because it contains descriptions of personal health matters, then say THAT, but do not say that someone asked for medical advice when they never did. --JWSchmidt 18:20, 30 October 2007 (UTC)

• Hey, why was my comment removed? All I said was that the original question did not seek medical advice. And that continues to be my opinion. The question was not describing a symptom -- "a sensation or change in health function experienced by a patient" -- because there was no implication that the questioner's health was affected. They were just curious about Hair follicles, a subject on which the Wikipedia article is B-class at best. --M@rēino 04:23, 31 October 2007 (UTC)

This is plainly ridiculous! The sense of this regulation is to avoid unqualified suggestions to be accepted and considered professional by the user. How should this do any type of damage what so ever? If you apply that definition about a symptom it can be eligible to all sorts of things, to nausea due to boat movements for ezample. Aren't you allowed to explain the processes that occur in that event?! Laws and regulations should be implemented only when they make some type of logical sense. You're just tking it to the extreeme here.193.188.46.254 13:56, 31 October 2007 (UTC)

Membrane Potentials

What is the difference between membrane potentials, diffusion potentials and nernst potentials. I understand membrane pot. = diffusion pot. and nernst pot. to be when the electrical force opposes the concentration force.?

In biology, a membrane potential is the electric potential difference across a membrane of a cell or an organelle such as a mitochondrion. For charged ions there can be a balance between movement across a membrane due to diffusion and movement due to the electric potential across the membrane: see reversal potential. If you had a membrane and only one ion was able to cross it by passive diffusion then at equilibrium the membrane potential would be equal to the diffusion potential of that ion: Nernst Potential. --JWSchmidt 14:29, 30 October 2007 (UTC)

Thanks for the quick reply. I have a slightly better understanding now but still wich to clear some issues [this is in the context of the establishment of an RMP]. 1) Does the term diffusion potential apply to an ion or membrane? 2) Could the Nernst potential (equilibrium potential) be described as the potential difference required to prevent net diffusion of that ionic species? (and how is Nernst potential related to diffusion potential?) 3) What is the purpose of the Na/K ATP'ase (it contributes slightly by reducing RMP; is its primary function to repolarise?). Thanks.

[ATP'ase] I thought a bit more and reasoned that the purpose may be to create the diffusion potential? or allow the tissue to become excited (function)? i.e. to maintain concentration gradient thereby preventing the Nernst potentials for each ion (Na/K) being reached (a scenario where membrane potential- or is that diffusion potential- is a result of only Na and K)

Did you find Resting potential? For most cells, the Na+/K+-ATPase is not thought to make a major contribution to the resting membrane potential. The resting potential of many cells is close to the equilibrium potential of potassium ions (K⁺). Many cells have potassium "leak" channels that control the resting potential. --JWSchmidt 18:13, 30 October 2007 (UTC)

When will oil run out?

Based on world wide consumption trends, and ignoring that it takes millions of years to produce more oil. 64.236.121.129 16:04, 30 October 2007 (UTC)

It will never "run out" - but it will become far too expensive to use as fuel. When? See Peak oil. Cheers Geologyguy 16:06, 30 October 2007 (UTC)

I did some calculations in response to an earlier question - the answer is that if we were to carry on consuming it at the present rate, it would run out in about 500 to 600 years. However, if we actually did that, the CO2 levels in the atmosphere would be far beyond "mere" global warming problems - they'd be at a point where humans (and most animals) couldn't breathe. However, the assumption that we'll carry on using it at present levels is flawed. I don't think that running out is a practical proposition. Even if we somehow managed to 'sequester' the CO2, we would only have to halve our consumption every 250 years in order to make the stuff last forever. Another issue is that these numbers for oil reserves are always accompanied by a caveat that says "economically retrievable" - in other words, the only things the oil companies care about is the stuff they can dig up for less than they can sell it for. There are reserves of stuff like "oil shale" that contain a lot of oil - but which are so expensive to dig up and refine that it's not worth doing it. If the oil were ever seriously likely to run out, then the price would go through the roof and suddenly oil shale (or whatever) would be worth exploiting and our reserves would increase (although the price would still be astronomical by today's standards). However, we must stress that with what we know about global warming, it's all completely irrelevent. We must not ever come even close to running out - because even a tenth of that amount of oil - when converted to CO2 - would kill the planet. SteveBaker 16:28, 30 October 2007 (UTC)

Our article on world energy resources and consumption says that the world's oil reserves are 5.7x10²² J, and annual oil consumption in 2005 was 1.8 x 10²⁰ J, so this gives a ratio of reserves to consumption of over 300 years. However, as Geologyguy and SteveBaker have pointed out, this is a rather meaningless figure. In reality oil prices will rise, and oil consumption will fall as alternative energy sources become more economically attractive, and global warming imposes a shorter deadline on us anyway. Gandalf61 16:44, 30 October 2007 (UTC)

Perhaps by then we will have made advances in scrubber technology, and have them on every car, big ones atop every building, and just generally all over the place. I mean, once it comes down to economy vs. survival... Arakunem^Talk 17:18, 30 October 2007 (UTC)

The chemistry of scrubber technology is not very promising - the kinds that merely absorb CO2 will give the gas up again fairly easily and the substances that react with CO2 to actually get rid of it require lots of energy to make in their own right - so you end up needing more scrubbers to scrub the output of the factory that makes the scrubbers (or the power station that drives it) than the factory itself can make. It's really a bad idea to pin one's hopes on such things because it distracts from the very critical thing of cutting CO2 production in the first place. The whole "Clean Coal" campaign (which has to rely on science-fiction "carbon sequestration" techniques) is a particularly bad example of this kind of wishful thinking. SteveBaker 03:40, 31 October 2007 (UTC)

Are you saying that collecting and burying CO2 from a coal plant won't work and will use more energy than you get from the coal?--Dacium 05:47, 31 October 2007 (UTC)

Yes and no. I'm saying that on small scales, it takes more energy than you get - and on large scales there isn't a viable technology for doing it at all. Not one single large scale CO2 removal/sequestration plant exists anywhere in the world - not even experimentally. (Which hasn't stopped the US from licensing the building of "Clean Coal" power stations - which is a scandal just waiting to get media attention!) Our article on Carbon capture and storage explains that what we're likely to have will remove 80 to 90% of the CO2 from the gasses and consume 10% to 40% more energy. But the biggest problem is what you do with the stuff once you've captured it. Sequestering it into limestone requires 180% more energy - so that isn't going to fly. If you try to sequester the CO2 without chemically converting it to something else then you've still got to find a place to store millions of tons of something that's a gas at normal temperatures and pressures. That's no easy task. You can't store it underground or underwater because there isn't enough space at normal temperatures and pressures (If you burn a cubic meter of oil or coal - you get a LOT more than a cubic meter of CO2 as a result! So pumping it into disused coal mines and oil wells isn't going to work for very long.) If you compress the CO2 so it takes up less space (eg storing it as dry ice), then that requires either very high pressure storage or very low temperatures. Either of those technologies will require yet more energy - and worse still, will be vulnerable to long term corrosion and other damage - so you're just building up more trouble for the future. There is talk of dissolving the stuff into saline aquifers or deep oceans - but those are not permenant solutions (eventually, the CO2 would get out again) and the resulting carbonic acids would likely do untold amounts of damage to the environment. Dealing with radioactive waste from a nuclear power plant is EASY by comparison because so little material is involved. So, no, we aren't going to be doing this if we want to save the planet. We have to cut down our consumption (probably the easiest thing to do in the short term) and switch rapidly over to nuclear and (where possible) wind/solar/tidal power until we figure out how to make fusion reactors that actually work. SteveBaker 18:00, 31 October 2007 (UTC)

On the scales you are talking about, I would imagine there would be nowhere near enough suitable locations to bury CO2 and be reasonably sure that it won't escape at some point in the future. Hopefully within 300 years we will have managed to develop alternatives to fossil fuels, otherwise our pathetic species probably doesn't deserve to survive. Bistromathic 16:41, 31 October 2007 (UTC)

Quantum foam

I was thinking about Quantum foam last night. Since particle/antiparticle pairs emerge out of the vacuum - and since there is no "rest frame" - it seems like the particle pairs must be travelling at random velocities relative to my motion. This implies that they have random kinetic energy relative to my motion - which means some of them must be arbitarily energetic. How come we don't measure them? Even though they only last for a spectacularly short amount of time in their own frame of reference - in mine, they'd spend an eternity recombining. Our article briefly sketches over that. SteveBaker 16:45, 30 October 2007 (UTC)

You are taking the idea of virtual particle pairs too literally. Quantum foam is a broad term for the fluctuating nature of space-time at a quantum level that theory demands. Those fluctuations are abstractly described as virtual particles, but from the practical point of there are no particles. Imagine a tablecloth with marbles on it. The marbles may move because they are hit by other marbles, or they may move because the tablecloth shakes. If all you could ever see were the motions of marbles, you might try to explain the motions caused by shaking in the tablecloth as being caused by invisible "virtual" marbles. What is going on in physics is similar. The ways that real particles are affected by the quirks of the vacuum can be usefully described by replacing the vacuum with infinite numbers of virtual particles constantly bombarding matter. However, those particles don't really come from anywhere or go anywhere. They don't have an existence that one could isolate and interact with individually. Really, they are collectively just a way of describing the manifestations of the complicated quantum mechanics intrinsic to space-time. Dragons flight 19:55, 30 October 2007 (UTC)

Steve, "quantum foam" does not refer to the virtual particle/antiparticle pairs in the quantum vacuum in general, but specifically to what happens around the Planck scale, where spacetime becomes quantum mechanical. The short answer to any question about quantum foam is that we don't know anything about it at all. But I think you're asking about the quantum vacuum in general, so let's step back from solving quantum gravity and consider something more manageable. Take QED or Klein-Gordon theory. You asked "How come we don't measure them?", referring to virtual pairs with arbitrarily large energies. OK, how do you want to measure them? You would have to interact with them somehow. That means that instead of a vacuum-bubble diagram, you have to consider diagrams with external vertices, and virtual particle loops inside. One way to think about these diagrams is that your real external particles are encountering the virtual particles from the vacuum; and they can indeed have arbitrarily large momentum and energy. In many quantum field theories, these loop contributions cause all calculations to come out infinite. Similarly, the vacuum diagrams can cause the vacuum energy to come out infinite. To get something physically sensible, you have to renormalize the theory, and "renormalize" the vacuum energy by zeroing out the infinite offset. So even if you never observe the virtual particles as discrete events, they are hugely significant in every interaction between particles! In some theories, like supergravity, the case is even worse than that, and renormalization doesn't work. Because all of this is not very intellectually satisfactory, we hope that there is some real, underlying physics that doesn't have these problems. Supersymmetry takes care of the infinite vacuum energy, but still needs renormalization. Superstring theory attempts to avoid the need for renormalization at all. But now we're back in the realm of speculations about quantum gravity. --Reuben 21:49, 30 October 2007 (UTC)

Why don't they put some kind of grating over jet engine intakes to prevent birds from getting sucked in?

Why not? 64.236.121.129 16:57, 30 October 2007 (UTC)

It probably doesn't happen all that often and may actually cause too much disruption to the air intake on the engines. Also, birds would still (I imagine) be sucked and stuck to the grating over the intake. -- MacAddct1984 17:05, 30 October 2007 (UTC)

Per MacAddct, a grating would seriously disrupt the airflow into the engine, creating a tremendous amount of drag. (Remember that air is flowing through the engine at several hundred kilometers per hour.) Plus, what if the bird strike actually damages the grating? In addition to having a bird in the turbine, you'd get all those jagged metal bits of broken grating.... TenOfAllTrades(talk) 17:12, 30 October 2007 (UTC)

No - there is no grating - but there is a requirement to test engines for bird strike damage. They actually have an air-powered cannon to shoot birds into running jet engines in order to test them. However if you fly at high speeds and lower altitudes (where birds tend to be) - and if you hit a big one - you can certainly throw a turbine blade and utterly trash the engine in the process. If you have a strong stomach - read Bird strike which has some exceptionally grisley photographs of the effects of birds on airplanes and airplane engines in particular. SteveBaker 17:35, 30 October 2007 (UTC)

Yep. Even with a no-drag indestructible grating, you're still talking about smashing a bird into something at several hundred miles per hour. It's not that the engine is sucking in birds from all directions, just that the plane and bird are hitting -- and even with a grating, the engine still has to generate the same suction. But as SteveBaker said, there's a bird strike test, so a grating is superfluous. — Lomn 18:18, 30 October 2007 (UTC)

A bird running into a turbine is usually not dangerous. The bird will be ripped apart. If the turbine does throw a peice and destroy itself, all that happens is that fuel will continue to be pumped in and a massive flame will come out the back because the fuel is being burned. Obviously you get no thrust from the engine, but the plane can still fly. I don't think any commercial airliners have been brought down, many have had engines taken out.--Dacium 05:43, 31 October 2007 (UTC)

According to Bird strike: according to the FAA only 15% of strikes (ICAO 11%) actually result in damage to the aircraft. But you're wrong about commercial airliners - there is at least one instance: Eastern Air Lines Flight 375 flew into a a flock of small birds that took out three out of the four engines at once - at the critical moment just after take-off when the engines were at full power - they also splattered over the windshield - blocking the pilot's view and clogged the pitot tubes, preventing them from knowing their airspeed. They didn't stand a chance - the plane rolled over and smashed into the ocean - there were 62 fatalities out of 72 people aboard. Our article on bird strikes also says: the problem costs US aviation 600 million dollars annually and has resulted in over 200 worldwide deaths since 1988. We have a brief article about Birdstrike simulators too! SteveBaker 17:31, 31 October 2007 (UTC)

Taste bud abnormality

I was wondering if there is a name for the painful bumps that crop up on tongues from time to time. It seems as though a single taste bud turns white, enlarges, and becomes very sore to the touch. I can't seem to find a name for it anywhere (and no, it's not herpes or canker sores) -- MacAddct1984 17:10, 30 October 2007 (UTC)

Sorry, but this question is basically asking for a diagnosis, which we aren’t allowed to do here. As it says at the top of the page:

Do not request regulated professional advice. If you want to ask advice that "offline" would only be given by a member of a licensed and regulated profession (medical, legal, veterinary, etc.), do not ask it here. Any such questions may be removed. See Wikipedia:Medical disclaimer and/or Wikipedia:Legal disclaimer. Ask a doctor, dentist, veterinarian or lawyer instead. MrRedact 17:33, 30 October 2007 (UTC)

While MrRedact is correct that we can't diagnose, you might nevertheless be interested in the brief stub on lie bumps. It could stand to be filled out if you want to do some source research. --Trovatore 17:36, 30 October 2007 (UTC)

Ah, thank you very much Trov! While I wasn't really looking for medical advice, I do realize there is a very fine line between "diagnosing" and what I was asking. But that is what I was looking for, I remember my mother always saying the old wife's tale was that you get them when you lie. -- MacAddct1984 17:53, 30 October 2007 (UTC)

I can't say what this is in your case, but it also happens to me when I accidently scrape the area with a sharp piece of food or bite the tongue. Here's an article that discusses lie bumps a bit more: [16]. Again, this may not be what you have though. Sancho 17:47, 30 October 2007 (UTC)

they are basically caused by cuts in the tongue by food or your own teeth. If they are on the edge of a tongue it almost defiantly is caused by you biting your tongue accidentally. usually a mouth full of food pushes the tongue over the teeth and people bite without realising.--Dacium 05:38, 31 October 2007 (UTC)

how do i make my dog smart

please thank you —Preceding unsigned comment added by 77.234.83.173 (talk) 17:19, 30 October 2007 (UTC)

See dog training. Sancho 17:38, 30 October 2007 (UTC)

I don't think you can change your dog's intelligence - as with humans, it's pretty much something that you're born with - but you can certainly enroll in a training course for you and your dog. Sadly, it generally turns out that your dog is plenty smart and it's you that gets trained - but that works too! We also have an article on Dog training. I have two dogs - one smart (female), the other dumber than a bag of hammers (male). The smart dog has learned to bark at the front door when she wants to be let in. The stupid dog has not. He just stares at the door hopefully. However, the smart dog has realised this and when she sees him standing there looking puzzled, she runs up to the door, barks until we open it and let him in - then she goes back to whatever she was doing before. SteveBaker 17:43, 30 October 2007 (UTC)

Intelligence can most certainly be changed in humans. And it's important that people are aware of that. There was a study recently that took two classes of high-school students, gave one a lecture about something boring and irrelevant (just to have a control), and gave the other a lecture on the nature of intelligence, and how intelligence and problem solving skills can be improved through training. After about half a year the second group showed a significant increase in grades and the first didn't. Of course there is always the criticism that training intelligence is just training for intelligence tests, but I believe strongly that intelligence by any reasonable definition can be consciously improved. I see no reason why dogs couldn't do the same, except that they probably won't have the mental capacity for defining the concept of intelligence, so they can't set it as a goal for themselves explicitly. Still, if you set out a wide range problem solving exercises with rewards that the dogs can understand (like the 'stack boxes to get to a banana'-kind of exercises they give monkeys, only simpler), they may generalize over all exercises and improve their problem solving intelligence instead of just learning specific tricks. risk 18:16, 30 October 2007 (UTC)

thats a lot of reading, what's something simple ic an do like some toy i can buy or music to play. i cant afford obedience school. —Preceding unsigned comment added by 77.234.83.173 (talk) 18:09, 30 October 2007 (UTC)

There are no magical shortcuts. If you can't afford obedience school - read our Dog training article carefully and do what it says - it's pretty much what the obedience schools teach. Set aside an hour a day for training. Make sure your dog knows that this is something special - "Now is training time - later will be play time" - so have a special routine you go through at the start and end so your dog will come to recognise that. SteveBaker 00:08, 31 October 2007 (UTC)

I have an instinctive negative reaction to the idea that learning to obey demonstrates intelligence. I've always sort of felt that cats are smarter than dogs, precisely because they don't obey you. --Trovatore 01:33, 31 October 2007 (UTC)

Dog training is more about learning inter-species communication than obeying orders. I prefer to think of it as unlocking the intelligence that was always there - and in a way that we humans can understand. SteveBaker 03:25, 31 October 2007 (UTC)

I don't know about smart but I made my dog smarter with this and this and this. All three are essential. --DHeyward 05:40, 31 October 2007 (UTC)

Get involved with Dog agility or Flyball. You and the dog have fun; you and the dog get to socialize; you and the dog get good outside exercise; and the dog's intelligence is developed. It's mostly just run by volunteers, so there's little cost.--Eriastrum 17:06, 31 October 2007 (UTC)

When you here about plane crashes on the news

They usually manage to find the Black Box flight recorder thing even in the worst crashes, when the rest of the plane has been completely destroyed by explosion and fire. So, why don't they make the planes out of the same material they make the black boxes out of? --84.68.112.172 17:50, 30 October 2007 (UTC)

While black boxes are of durable construction, I think they benefit a great deal by being inside the aircraft. By analogy, I could get into a car wreck that's bad enough to total my car, but it's likely that my CD player would survive. It's not that it's made of some magic substance—it's just protected by the body of the car, which can deform and break up, absorbing a lot of impact energy. -- Coneslayer 17:57, 30 October 2007 (UTC)

In short, the black box is so heavily armored so as to survive the worst impact, that if the airplane was made similarly, it would be more like a tank than an airplane, and would be too heavy to fly. Planes are made to fly, CVR's are made to crash, as "they" say. :) Arakunem^Talk 18:03, 30 October 2007 (UTC)

Check out this classic Cecil Adams column. "If aircraft "black boxes" are indestructible, why can't the whole plane be made from the same material?" 69.95.50.15 18:01, 30 October 2007 (UTC)

It's also worth noting that an indestructible airplane would provide little extra protection to all-too-destructible passengers, who are still independently subject to the laws of inertia. Crash casualties are not so much the product of a deforming airframe as they are of a sudden stop. In fact, the deformation is good -- it absorbs crash energy that would otherwise injure passengers even more. Modern cars are constructed with this same theory in mind. — Lomn 18:12, 30 October 2007 (UTC)

I wonder if the querent is looking for material for a stand up comedy routine? According to our article, Flight data recorders tend to be "double wrapped, in strong corrosion-resistant stainless steel or titanium, with high-temperature insulation inside." We don't make jetliners out of titanium for the same reason we don't make windows out of diamonds, its not cost effective (though, as an aside, while the SR-71 Blackbird was made out of titanium, its windows were not diamond), and if we packed it full of high-temperature insulation, where we would put the passengers? Rockpocket 18:14, 30 October 2007 (UTC)

Also, black boxes aren't black - they're orange. SteveBaker 00:04, 31 October 2007 (UTC)

Depends on how hot the fire is. --DHeyward 05:09, 31 October 2007 (UTC)

Even if the plane were made to survive a crash, it doesn't help people inside. Say the plane can survive 1000G of force, your body cant and you would be squished to death on impact, regardless of if the plane body deformed or didn't. The best solution for safety would have to be a plane that deforms enough so that a +100G impact is reduce to say 10G.--Dacium 05:50, 31 October 2007 (UTC)

Digitap imaging & printing

perfect on screen but when i printed it on my Epson stylus Photo RX620 it looked nothing like what it did on screen. I was truely gutted. It was duller, darker, more saturated & lost a lot of fine detail. I am using the correct paper & my ink channels settings are set to default. This is happening with all of my images.

Why is this happening & how can i resolve it so that what i create on screen prints as it looks on screen? Also what is the difference between a jpeg, tiff, Esp, btmap etc?

Thanks kindly

Nay —Preceding unsigned comment added by 86.145.223.206 (talk) 19:33, 30 October 2007 (UTC)

For the latter, articles such as JPEG, TIFF, and BMP file format may be of use. For the former, I have no suggestion apart from experimenting with configuration settings (as this is not so much a case of correctness as one of preference). — Lomn 20:05, 30 October 2007 (UTC)

You may find this is better answered on the computing reference desk however I'll have a quick stab. Computer screens use additive colour. They add red, blue and green colours together to make white. Printers OTOH use ink which substracts colour. They use cyan, yellow and magenta and mixing them together makes black :-( So the screen will never look the same as a printer.

Also ink jet printers use wet ink thqat runs a bit and the colours bleed together making it dull. Having a good quality laser printer and using top quality paper will definately produce crisper and brighter prints. Fortuately the cost of colours lasers has been plummeting in recent years Theresa Knott | The otter sank 20:10, 30 October 2007 (UTC)

There are many problems here. Additive versus subtractive, impure inks and toners, the fact that you are printing in four colours (Cyan, Magenta, Yellow and Black) instead of three, that the printer needs to use dithering and bleeding of inks to do what it does, that the brightness of your screen is independent of the room lighting - but the brightness and hue of your print is entirely dependent on the colour of the ambient lighting - that the software that does the conversion is rarely correctly set up for the kind of paper you are using - that the gamma of cameras and screens are NEVER correctly set up, that not all programs take notice of the gamma values that the camera put into the file header - and if you save the picture out in another format, that information is almost certainly lost, that our eyes respond differently to a pigment that reflects yellow (meaning a true yellow) versus a seemingly identical pigment that reflects both red and green, that your CRT probably has several different colour temperature settings and you have no clue which one you picked...there are a million reasons. The bottom line is that you're doomed and you just have to tweak the available settings until you get it "how you like it". (There is no "Right"). SteveBaker 23:50, 30 October 2007 (UTC)

Oh - and the difference between various file formats (for the purposes of this discussion) are that JPEG and GIF both compromise the true colours of your photos in order to save a lot of memory. 24 bit TIFF and PNG can store colours in their original perfection with no losses whatever. BMP (urgh) can go either way - and it's a horrid format anyway so don't use it. The various 'raw' formats that cameras sometimes use are better still - IF you have the right software to handle them. There are some esoteric formats that do even better - but I doubt you'll ever come across them. On balance:

• Use PNG for original artwork and photos stored on your computer at home - where (presumably) you have plenty of disk space.
• Use RAW images for original photo archives if your camera and software supports them - but convert to PNG for day-to-day use.
• Use JPEG for photographic types of pictures on the Internet - it's compact - which means it downloads quickly - and the losses due to it's compression tricks are not noticable on a typical browser at the default screen resolutions we have these days. As broadband starts to conquer the world - I'm going more and more towards using PNG even in these situations.
• Use GIF only on really high usage web pages for cartoony stuff or (if you absolutely must) for animated images.
• Don't use TIFF or BMP if you can possibly avoid it - they are both only patchily supported in areas like gamma that truly matter.

SteveBaker 00:01, 31 October 2007 (UTC)

Mom Haircut

Okay, this is a stretch, but I'm going to try it anyways... just bear with me, okay?

Is there a condition or an illness (for lack of a better word, I don't mean to imply bad health) that would describe the tendency for new mothers to get a drastic haircut? I don't mean the "mom haircut" but, just even like dying it a different color, something that makes a dramatic change. I know this could just be associated with going through major changes in their life or, more dangerously, depression, but I was wondering if there was a name for it specifically. Thanks, and I apologize if this question is just too dumb for words. Beekone 20:18, 30 October 2007 (UTC)

You might find more information under the mid-life crisis article -- MacAddct1984 20:43, 30 October 2007 (UTC)

One could argue it is an evolutionary successful strategy: long hair is an energy intensive characteristic adopted by females to attract a mate. After pair bonding and generating offspring, the female no longer considers the energy invested in maintaining long hair is no longer required, hence they cut it. Or it could be that they don't want to get nits from all the little brats they interact with. Or it could be to reinvent themselves for the next stage in their lives, or it could be part of an effort to "look good" again after the physical changes associated with child birth. Interestingly (or not) there does seem to be some recognition of "mom hair" in the mommy blogosphere, but its extremely unlikely that it has a specific biomedical name. Rockpocket 20:45, 30 October 2007 (UTC)

I'm not even sure what you are describibg is a real phenomenom. Is there any data to suggest that on average new mums get more dreastic haircuts than women of that age who are not new mums? Theresa Knott | The otter sank 20:52, 30 October 2007 (UTC)

No, I'm not sure such research exists... I guess that's why I asked. It seemed like a funny quirk that I'd noticed in some friends and acquaintances. I agree that the likelihood of this activity having a specific medical name is extremely un, but you never know until you ask, right? Beekone 21:05, 30 October 2007 (UTC)

Googling "mom haircut" at least provides evidence that the "mom haircut" is culturally believed to be a real phenomenon. From reading the various pages, it sounds like a "mom haircut" is either quite short, or long and tied back. In either case, it sounds like the point is to have a low-maintenance, no-nonsense haircut that isn’t going to get in the way of the harried new mother, who suddenly has less time for dealing with such frivolities as hair. MrRedact 21:30, 30 October 2007 (UTC)

Don't think anyone has mentioned the obvious answer (well, obvious to anyone with practical experience of babies), which is that babies of a few weeks and older love to practise their hand-eye co-ordination by grabbing and pulling long hair. Gandalf61 10:39, 31 October 2007 (UTC)

"I don't mean the "mom haircut" but, just even like dying it a different color, something that makes a dramatic change. " signed, the very first post! Read, think, reread, comprehend... maybe Beekone 13:04, 31 October 2007 (UTC)

You start off with: "Is there a condition or an illness ... that would describe the tendency for new mothers to get a drastic haircut?" If you are going to ask contradictory questions, you are going to get contradictory answers. Rockpocket 17:14, 31 October 2007 (UTC)

How does "drastic haircut" translate into "mom haircut"? I mean I know I called the topic that, but I state repeatedly that that's not what it's about. To be technical I start off with this: "Okay, this is a stretch, but I'm going to try it anyways... just bear with me, okay? " 'Clearly the message is going to be muddled so I should pay close attention,' thought the reader. Beekone 17:18, 31 October 2007 (UTC)

Additionally, I liked your answer, Rockpocket. You seem to get what I was asking, and correctly stated that such a condition is unlikely to have an actual label. But at least you got what I was asking, even if you're answer was basically "I don't know." The other answers are "I don't know" plus a hint of "I obviously didn't try to get what you were asking" which i frustrating because if you don't know why even answer? Just pass it by. I obviously asked in the case that someone with knowledge of the topic might answer. It's sort of what the Help Desk is all about... in my understanding anyways. Beekone 17:23, 31 October 2007 (UTC)

Why don't they use water jets on very large ships?

The largest they used it on was a frigget I think. Why not larger ships? 64.236.121.129 20:26, 30 October 2007 (UTC)

Our article on pump-jets notes some of their advantages, contrasted with a decrease in efficiency versus propellor-based designs. In particular, the note about power density may be relevant, as frigates don't have as much hull volume to fill with engines as do destroyers or cruisers. The shallow-draft advantages provide additional merit for new littoral combat ships. At some level, though, the lack of adoption may simply be industrial inertia. Propellors are well-understood and consequently are considered to inherit less risk than a relatively new technology like pump-jets. In the absence of a compelling advantage for the latter, then, the former is likely to remain in widespread use. — Lomn 20:36, 30 October 2007 (UTC)

Many very large ships still have bow thruster jets.--Dacium 23:54, 30 October 2007 (UTC)

Sugar in Soda

I've decided to eliminate soda from my diet. While shopping at a local grocery store, I came across a powder lemonade product that one mixes with water. The lemonade’s packaging said it "contained 40% less sugar than soda." So with everything being equal between the soda and the lemonade (calories, fat, etc), what would be the benefits of 40% less sugar? I would assume that there would be some benefits…or is this a fancy marketing ploy?

Thanks 64.85.199.27 20:41, 30 October 2007 (UTC)

It's precisely a marketing ploy. Whether it actually benefits you depends entirely on your diet. People hear that carbs are bad, carbs make you fat, so they advertise that they have fewer carbs. Sugars/carbs are the normal person's primary source of energy, and it is the first form of energy (calories) the body will burn in order to operate (fats it prefers to store away). Now, if the food in your diet contains all the calories you need in a day, and you just want something to quench your thirst, there's really no need to drink something laced with sugar that will just get converted into fat for long term storage, so you may as well go for that low-sugar lemonade. Someguy1221 20:47, 30 October 2007 (UTC)

(ec)Soda contains a lot of sugar! 40% less means 60% still remaining which is still very bad for your teeth. Having said that soda contains not fat, protein etc. It's water and sugar, so 40% less sugar will be 40% less calories. Those calories that remain are junk food calories though. Much better to drink water or tea. Theresa Knott | The otter sank 20:49, 30 October 2007 (UTC)

Also, the drink may have had that 60% of sugar boosted by an artificial sweetener, and if you read sugar substitute you'll see that all the common ones have some kind of controversy about potential health risks attached. Confusing Manifestation 21:39, 30 October 2007 (UTC)

Just drink diet or zero soda's (diet coke, coke zero, pepsi max etc). These contain zero suger. Also other things that are high in suger are sauces like ketchup, alcohol etc. Personally I would try to ditch soda all together and drink water. Try drinking two classes of water before you eat.--Dacium 23:27, 30 October 2007 (UTC)

There are two very different things being talked about here. Diet Coke/Pepsi/whatever contains almost zero carbs. Giving up Diet coke and drinking this stuff will increase your carbs by a large percentage because their claim to have less carbs than "Soda" is a poorly worded and highly misleading statement. WHICH soda do they have 40% less than? If has 40% less than one of those insane "energy drinks" (Mountain Dew MDX for example) then it probably has more sugar than Classic Coke too! Different kinds of soda have everything from zero sugar up to (probably) the maximum amount that'll stay dissolved in water without crystalizing out! It's nothing to do with whether it's carbonated or not. So if you need to reduce your sugar intake, switch to a diet soda. If you are concerned about the CO2 in the soda - then switch to a non-carbonated beverage. But don't give up either "just because". Read the ingredient list and compare the actual numbers - forget the silly marketting percentages. Think about what you are really doing! As others have mentioned, if you get your total carbohydrate intake down to zero - you'll get seriously ill amazingly quickly of something called "protein poisoning" (aka Rabbit starvation). SteveBaker 23:39, 30 October 2007 (UTC)

Actually sugar will dissove in huge amounts in water without crystalising out. I suppose the max would be something like golden syrup but you would't drink that. Theresa Knott | The otter sank 00:35, 31 October 2007 (UTC)

Will it fly?

I say yes, and so does straightdope, but what is the answer????--Goon Noot 23:08, 30 October 2007 (UTC)

Yes it will. Airplanes move due to thrust from the engines, not torque from the wheels. The plane's wheels will just be spinning at 2x the takeoff speed when it leaves the ground. Arakunem^Talk 23:11, 30 October 2007 (UTC)

I say nay. There is no lift because the plane isn't moving forward.

It is moving, but it is on the treadmill, and the treadmill isn't moving forward.

strap that whole shebang on top of a car... then we're talking —Preceding unsigned comment added by 128.175.187.238 (talk) 05:59, 31 October 2007 (UTC)

-Stephen Hawking —Preceding unsigned comment added by 74.196.103.230 (talk) 23:15, 30 October 2007 (UTC)

It's an enormous treadmill, but the aeroplane's wings will be ripped off as it starts to fly. DuncanHill 23:17, 30 October 2007 (UTC)

In the original formulation of the question, the treadmill was infinitely long and the wheels completely free-running. The photo just confuses the question. The plane doesn't give a damn what happens to its wheels - they are free-running. Moreover, once it's engines are running with enough power to overcome the tiny amount of rolling friction in the wheels, the plane will take the same distance to take off no matter what speed the treadmill is running (forwards, backwards, who cares?). This one has been done-to-death and the answer is as clear and obvious now as it was at the beginning. I don't believe Stephen Hawking (or at least "The" Stephen Hawkin) said that. SteveBaker 23:21, 30 October 2007 (UTC)

It 100% will not take off. There is no way for it go gain lift. The plan engines thrust forth, pulling the wing, with the idea that the wing is pulled fast through the air, air goes over the wing and creates lift. There is no way for the plain to gain lift. People who think it could take off must also believe that a plane with no wheels could simply turn on its engines and hover up in the air.--Dacium 23:22, 30 October 2007 (UTC)

If you think about it, any plane is already on a giant moving treadmill. It's called the Earth. Remember that all motion is relative, so putting a plane on a treadmill moving with constant velocity is really no different from having a wind coming up from behind the plane. From the plane's perspective, it has to go a little faster to take off because of this wind. From your perspective, it takes off at normal speed, but it takes a little longer to reach it (since it started moving backwards with the treadmill) and the wheels will be turning faster. Now, you could also have the treadmill accelerating backwards at the same rate the airplane accelerates while taking off. In this case, the plane sits where it is, the wheels constantly speeding up, and the engines working to keep the plane exactly where it is (although, in that case, you could just turn the plane around and use the treadmill to launch it). Simply put, all motion is relative, being a treadmill won't have any greater effect on the plane than wind. Someguy1221 23:24, 30 October 2007 (UTC)

A plane moves forward by air entering the engines to create thrust. A plane has to build up it speed because there is only little thrust to begin with. As the plane gets faster, more air is entering the engine and the thrust increases. It is the air speed relative to the plane that is the only thing that matters. A plane could hover straight up in the air if the air speed was great enough. The treadmill stops the plane gaining speed relative to the air and stops it taking off.--Dacium 23:44, 30 October 2007 (UTC)

The plane still moves. Unless the treadmill is accelerating, the plane will eventually beat it and take off. Imagine the treadmill is massive, say, the Earth. Would the plane notice or care if the treadmill were moving? Not unless it's accelerating. So this is why I say, if the treadmill is moving backwards at 30mph, this is no different than a tailwind of 30mph. The plane has to speed up a little more (from its own perspective) to generate sufficient lift. But it is by no means prevented from moving. Someguy1221 23:49, 30 October 2007 (UTC)

Sorry I thought we were assuming the treadmill was accelerating to match the speed of the plain. Obviously if it doesn't the plain will still be able to gain speed relative to the air, and take off. So we are all in agreement then. Non accelerating treadmill - plain takes off. Accelerating treadmill - plane does not take off.--Dacium 23:52, 30 October 2007 (UTC)

The treadmill would have to have tremendous acceleration to slow the plane below its takeoff speed. (Remember, the wheels are free-wheeling. The only thing slowing the plane is double the normal amount of friction in the axles. The situation is nearly the same as if the plane had hovercraft instead of wheels. ) I'm pretty sure that a treadmill constructed to put out that sort of ridiculous acceleration would reach near-C speeds in a minute or two then the plane could still take off normally. 69.95.50.15 18:42, 31 October 2007 (UTC)

So I have this funny feeling I may have my relativity backwards on the accelerating part, someone please check me on that. Someguy1221 23:57, 30 October 2007 (UTC)

The wheels play zero part in generating forward speed. The engines react against the air to generate forward thrust. The treadmill could be going faster in "reverse" than the plane is moving forwards, and it will still move forward. The wheels would be spinning reeealy fast backwards but thats irrelevant to this. Arakunem^Talk 23:33, 30 October 2007 (UTC)

It all depends on how you define the question. If the airplane's wheel bearings are frictionless and the wheels themselves are inertialess, then it doesn't matter what the treadmill does: the airplane's engines will move the airplane forward and it will take off. If the wheels have rotational inertia, or the wheel bearings have friction, and the treadmill is allowed to adjust its speed without limit, then it is possible to use the friction or rotational inertia of the wheels to counter the thrust of the engines, and the airplane won't take off. --Carnildo 00:03, 31 October 2007 (UTC)

I think it's best to assume the plane is just a normal plane, with normal wheels. Someguy1221 00:08, 31 October 2007 (UTC)

Say a big plane like in the picture takes off at about 150mph, do you think it could take off with a 150mph tail wind? I don't think so. So imagine the treadmill is already travelling with the plane on it at 150mph backwards, can the plane take off? I don't think so. Now imagine the plane and the treadmill both start at 0mph, can the treadmill accelerate the plane backwards as fast as the plane accelerates forwards? I don't think so. At the very start of the plane's acceleration as the engines spool up a considerable amount of the thrust would be used to overcome the friction in the wheels, but very quickly as the thrust increases, I think the treadmill would have to travel MUCH MUCH faster backwards then the plane accelerates forward for the friction of the wheels to act as a break on the plane's forward acceleration, otherwise the plane will come to speed and take off, just with very fast spinning wheels. Vespine 00:54, 31 October 2007 (UTC)

Yes, if the treadmill is allowed to transfer enough net force through friction in the wheels it could hypothetically keep the plane stationary. If the plane is stationary with respect to the air, it will not take off, since lift depends only on the plane's speed with respect to the air. Dragons flight 00:57, 31 October 2007 (UTC)

Just to straighten things out hopefully. Assume still air (no headwind or tailwind). If the conveyor belt/plane contraption is set up so that the plane remains motionless relative to the air (whether or not the conveyor belt, wheels, or engines are going) the plane will not take off as no air is moving over the wing generating no lift. If the plane is moving forward relative to the air, it could take off. Another way to think about this problem is to envision a plane on a conveyor belt that pushes the plane forward while the plane's engines are off and the wheels not rolling at all. Will the plane take off? Yes, because air is moving past the wings generating lift. (Of course to maintain flight it needs the engines, but that is besides the point) Or you can envision it this way: with a strong enough headwind, a plane perfectly at rest could take off although to a stationary observer on the ground, the plane would be moving backwards while acquiring altitude (i.e. moving in the direction of the wind). I hope this helps. Sifaka ^talk 03:59, 31 October 2007 (UTC)

No, it will hit the handrails of the treadmill. (Darn, DuncanHill beat me to that answer :P)-- Diletante 01:10, 31 October 2007 (UTC)

It's worth noting (belatedly) that we did this question to death back on May 21. —Steve Summit (talk) 01:31, 31 October 2007 (UTC)

More importantly, would a bird flying in front of the treadmill get sucked into the plane's engine? Rockpocket 01:39, 31 October 2007 (UTC)

Yes because the engines are drawing in air. 71.226.56.79 04:02, 31 October 2007 (UTC)

If the treadmill matches whatever the speed the plane can do, then surely it would stir up a huge surface headwind wouldn't it? Voilà, there's your moving air. --antilived^{T | C | G} 07:09, 31 October 2007 (UTC)

A treadmill moving at 100 or 150 mph wouldn't stir up that much of a headwind. (And stop calling me Shirley.) —Steve Summit (talk) 12:01, 31 October 2007 (UTC)

It won't take off because there's no airflow around the wings! That's the whole point of why you need a runway for an airplane. You could say the Earth is a giant treadmill, but the air moves with the earth, and so do we. Air does not move with the treadmill. I'm surprised some of the people here thinks it will take off. It really makes me doubt how credible they were to answer my question about the ducted fans aircraft. Maybe it will take off if you have a powerful fan in front of the plane, but then you don't need a treadmill in the first place. Just thrust against the wind. 64.236.121.129 13:23, 31 October 2007 (UTC)

Aww you're mad *pats your head. You're also thinking of it wrong. I'm not going to bother explaining it because your last few posts prove that you aren't interested in listening. *pats your head*. Just because you don't understand it, doesnt mean it isnt so. Now you run on back to Starcraft lil guy —Preceding unsigned comment added by 207.67.148.212 (talk) 15:49, 31 October 2007 (UTC)

As I thought I made clear in my Earth/treadmill analogy, the only point of that is to dispel any belief that frame of reference is important. The only difference the plane cares about is the relative wind speed. Someguy1221 17:11, 31 October 2007 (UTC)

Actually, this is quite backwards. It takes off fine from a treadmill under the generally stated conditions (the treadmill moves at the same speed as the aircraft). Carnildo raises a good point that wheels aren't frictionless, and if you allow the treadmill to run so fast that the airplane is stationary, then it won't lift off (probably -- you're left with a weird feedback cycle). Thus, the key point of properly stating your constraints and assumptions is illustrated. On the other hand, a stationary aircraft in front of a fan can lift off, but as soon as it's no longer in front of the fan, it crashes due to the rapid change in airspeed over the wings (as opposed to the treadmill liftoff, in which the aircraft flies away normally).

In a related question, A friend once suggested to me that the real issue in this situation would be that the wheels would be turning at double their normal RPM (obviously). He suggested that the tires on many jets are not rated for those RPMs and would destroy themselves before the plane went airborne. Is this true? Stated more clearly, if a 747 was placed on a treadmill like the one described so that its wheels were always turning at double the normally expected rate, would the plane survive takeoff? 69.95.50.15 18:36, 31 October 2007 (UTC)

With no true evidence, I'll say "probably". The wheels undergo significantly more stress at landing (going from no speed to 150 MPH or so very quickly) and have a sizeable engineering margin above that. Simply spinning on takeoff should be no big deal. — Lomn 19:13, 31 October 2007 (UTC)

For the consequences of a tyre failure on takeoff, see Air France Flight 4590. Admittedly, the tyre failed due to debris on the runway, but airplane tyres were subsequently redesigned. -Arch dude 22:25, 31 October 2007 (UTC)

October 31

Running hands under Superacid

After reading Superacids, what would happen if someone washed their hands under a tap of fluoroantimonic acid? How fast would the hands disintegrate? Acceptable 01:35, 31 October 2007 (UTC)

I guess it is unacceptable to post chromic acid stories? Delmlsfan 01:51, 31 October 2007 (UTC)

I once breathed in fumes of hydrogen chloride gas (by accident), not a very fun experience... -- MacAddct1984 14:02, 31 October 2007 (UTC)

Once it hits the water of your hand, it's no longer nearly as super. That is, it becomes little different than a really really concentrated solution of other acids (hydrochloric, sulfuric, etc) in regards to its acid effects. On the other hand (sorry:) the fluoro and stibbic components might present other hazards all their own. DMacks 02:01, 31 October 2007 (UTC)

Transporting rice

Car Talk's most recent puzzler was something along the lines of:

With old wooden ships, what common household item, if not stored properly, would sink a ship in a matter of minutes?

Apparently rice was the answer. If it wasn't stored properly and got wet, the massive amounts of densely packed rice would swell and split the ship apart. Has anyone heard of this before? It certainly sounds plausible. -- MacAddct1984 01:42, 31 October 2007 (UTC)

Car Talk got this information from the book Tall Ships by Philip McCutchan.[17] The author’s name is misspelled on Car Talk’s web site.[18] That book says "Spaced along the upper deck were the cargo hatches with their heavy covers of reinforced hardwood planks, well chocked in and secured with three separate layers of tarpaulin, held down with ropes and more chocks to withstand the pounding of heavy seas. Below the hatches lay the reason for the ship's presence on the sea, her cargo, to be held inviolate against nature and disaster, against fire that could come from a self-combustible cargo like wool, or a cargo that could swell when it met water, such as rice, which on more than one occasion in the long story of the sea swelled and in its irresistible pressure split the sides of holds like paper and sank those ships in minutes."

But that’s just what Philip McCutchan said. From the British shipping act in 1875, it sounds like the primary concern about properly storing grain on ships at the time was actually that the ship could sink if the grain shifted.[19] Maybe this is a question for MythBusters. MrRedact 03:25, 31 October 2007 (UTC)

I guess what bothers me about this is that once the water gets at the outer regions of the rice cargo, that will start to swell and the pressure build-up ought to lock out the water from getting in much further. But a lot depends on how fast the water is getting in and how fast rice swells. I guess it could be true. Definitely a good one for Mythbusters though. Car Talk's puzzlers are not exactly reliable sources of information! SteveBaker 03:32, 31 October 2007 (UTC)

This was a plot in a Horatio Hornblower book. He lost a prize of war. The ship was sinking even though no water was in the "well". It gains weight as well as stressing the hull. --DHeyward 05:18, 31 October 2007 (UTC)

For the locking question, I think osmotic pressure will keep sucking the water in to the center until they are all equally saturated. A dry rice grain next to water saturated one will suck the water out of it. --DHeyward 05:21, 31 October 2007 (UTC)

DHeyward: that was not a book, but rather the second chapter of Mr. Midshipman Hornblower. Algebraist 21:08, 31 October 2007 (UTC)

Children's vs Adult's voices

• What are the differences between children's and adult's voices, excepting the obvious physiological effects of growth and hormonal adjustments?
• For example, children's voices tend to sound more sing-songy, breathy, and rhymical, but have there been any studies to make quantitative or qualitative measures of the difference in voice-qualities as age progresses?
• It is obvious that human's are readily able to differentiate between younger and older speakers independently of any use of linguistic cues : are computers able to do the same, and under what heuristics would they operate?
• Are there any posited hypotheses of the cognitive causes of these non-physiologically determined variations?

Many thanks 81.153.3.36 10:05, 31 October 2007 (UTC)

I think this belongs in the section on Language and Linguistics. Meanwhile, I'm not well studied at all in developmental linguistics, but I can try to answer with what I know.

Obviously, as you stated, as a child gets older his larynx expands and produces deeper tones as the vocal chords vibrate. Similar resonance differences occur as the size of the oral and nasal cavity expand. However, the prosodic changes (those in rhythm and tone) can probably be traced to what are still not well understood phenomena in child linguistics. For example, a toddler will show reduplication (repetition of words) and other types of word play, depending on age, as he learns to speak. He will also exaggerate and misuse intonation (the parents do this too when they speak to children for the precise reason that intonation is difficult to master). All of this is most likely a result of the problem of learning something as complicated as language simply from cues around you. Computational models of this type of learning are very simplistic, last I've seen, and usually involve limited degrees of freedom (such as a simple robot learning to walk or play the drums according to outside information). None that I know of are linguistic in nature.

It is true that the age of a speaker can be approximated by linguistic cues alone. This is done in precisely the same manner as you mentioned, as well as by judging vocabulary, grammar use, pronunciation, and pragmatics (appropriateness of responses). Computers are probably most advanced at this point in distinguishing pronunciation, but still trained phoneticians are used to diagnose and treat speech disorders, because software simply still isn't good enough. The variations you discussed are not well understood computationally or anatomically, so I don't believe there have been any good hypotheses other than those suggested by experience with children. SamuelRiv 04:02, 1 November 2007 (UTC)

Things stuck in eyesocket

Suppose something small and mildly irritating (like, say, a bit of cat fur) got stuck up under someone's eyelid and worked up into the eye socket. What would happen to it? Would the body destroy it or expel it somehow? How long would it take? Maelin (Talk | Contribs) 13:16, 31 October 2007 (UTC)m n

In general, this idea falls apart when you expect something to work its way behind the eye. The eye, if I remember correctly, is pretty much sealed in the skull. There's no way to, for instance, lose a contact lens behind the eye. If you somehow DID get something behind the eye, it would have been through a wound, and the effects of that wound would be worse than the object itself, I should think. --Mdwyer 14:39, 31 October 2007 (UTC)

I guess it's possible something could embed itself up there and work its way in somewhat. I would expect a cat hair to be absorbed over a long period of time because it's protein, but anything inorganic...I shudder to think. And I suppose that the body would try to do to such a thing what it does to all such things, like splinters. The eye is different though; inflammation alone can be a serious matter. See sympathetic ophthalmia here and here. I doubt the body would have time to deal with an embedded cat hair before the eye reacted unfavorably to it. You can tell by my wishy-washy reply that I'm no expert. --Milkbreath 15:43, 31 October 2007 (UTC)

The function of the eyelashes would prevent a situation like this from occuring. Their job is to keep foreign objects out of the eye (i.e. dust, dirt, debris, cat hair). They work in conjunction with your tears to do it. Even though the primary function of the tears are to lubricate the eye, they also function as a sort of safety mechinism, when an object gets into the eye (be it dirt, dust, or cat hair) the eye gets irritated and tears up. The offender then gets caught up in the tears and then is eaither flushed out or it gets near the eyelid and caught by the eyelashes and taken out of the eye. Lastly, a thin, but strong, membrane, called the conjunctiva, lines the inside of your eyelids and curls back on itself to cover the white part of the eye. This prevents any obects from going behind the eye. Hope this helps! Josborne2382 16:18, 31 October 2007 (UTC)

I've gotten specks of dust stuck between my eyelid and my eye. That's not quite behind the eye, but I still wonder how it always ends up getting out, and how I could get it out faster. — Daniel 03:26, 1 November 2007 (UTC)

Hair loss

I asked my doctor about this but he didn't know exactly. I want to know if anybody has a link or two about uninterested reseaches on hair loss and effectiveness (if any) of treatments. I have quit given up hope on what constitutes medical advice so I'll just post fingers crossed and see if it gets deleted.193.188.46.254 14:03, 31 October 2007 (UTC)

The baldness article has a huge list of the various possible prevention/reversal treatments: Baldness#Preventing_and_reversing_hair_loss -- MacAddct1984 14:10, 31 October 2007 (UTC)

Freezing eye

Some time ago I read on how difficult it is for the eyes to freeze, but I forgot the reasons, could anybody patch me up on this? Also what would hypothetically hppend if you poured liquid nitrogen on somebodies eye? —Preceding unsigned comment added by 193.188.46.254 (talk) 14:16, 31 October 2007 (UTC)

I'd guess it is because they're salty, and salt depresses the freezing point. Still, LN is going to make them freeze anyway. Don't do it. :) --Mdwyer 14:34, 31 October 2007 (UTC)

It also helps that the human eye is embedded in a nice warm human being, equipped with all kinds of tools to maintain the body at a fixed 37°C. Heat is readily conducted from the back and sides of the eye socket (which, being right next to the brain, are well-supplied with nice, warm, constant-temperature blood) to the rest of the eye. Still, it would be possible to freeze the surface of the eye if you made enough of an effort—like by direct contact with a cryogenic liquid, for example. Tests in rabbit eyes gave the result:

Liquid nitrogen poured onto the eyes for one or two seconds with the lids held apart, produced no discernable injury. When the exposure was extended to five seconds, slight lesions of the corneal were observed. By the next day, all eyes were entirely normal.

I would expect longer exposure to do progressively more damage. Assumptions about the behaviour of human eyes based on the rabbit model should of course be taken with a grain of salt. TenOfAllTrades(talk) 18:43, 31 October 2007 (UTC)

Does it strike anyone else as odd that it is someone's job to pour chemicals into the eyes of rabbits? Man It's So Loud In Here 19:35, 31 October 2007 (UTC)

Rabbits are commonly used in animal testing. -- JSBillings 20:04, 31 October 2007 (UTC)

Not at all, how else would we determine the safety and efficacy of drugs formulated as eye drops? Rockpocket 20:21, 31 October 2007 (UTC)

Why do birds fly away from people?

I think this question is appropriate for the Science desk, since it seems to concern evolutionary biology. The question occurred to me this morning as I walked through a group of pigeons, which scattered as I approached them. This seems to be normal behaviour among our feathered friends, but when I stopped to ask myself why, I couldn't come up with an answer. In other words, why are birds scared of people? Of course, the answer that comes to mind first is that they are afraid of getting shot. Now, the chances of a pigeon being shot in a city street are pretty remote, although I guess the pigeon doesn't know that. So, is there some kind of evolutionary impulse at work here under which birds instinctively (and wrongly, in the case of city-dwelling birds) believe that man should be avoided? And if so, why hasn't this impulse atrophied among city-dwelling birds? --Richardrj ^{talk email} 14:25, 31 October 2007 (UTC)

Well, not just birds run away from humans. I can't think of any animal, unless it's a pet or trained, that wouldn't run away from a human. Humans are fairly big mammals, and if you saw something 10x the size of you, it's more than likely to benefit you to run away from it. Why hasn't the behavior atrophied? Probably because there is no selective pressure to fade out the trait. If running away from humans suddenly had a negative impact, such as they all started getting hit by cars when they try and fly away, then it's more than likely to weed out the trait. In the meantime, the pigeons have nothing to lose by flying away from approaching humans. -- MacAddct1984 14:39, 31 October 2007 (UTC)

Running/Flying away (Fight-or-flight response) is a pretty common behavior amongst animals. Not flying away from people is the unusual thing, probably bred into generations of city birds by the selective pressure of increased chance of food and less energy expense, as well as a lack of predators. Read about the Dodo to see what happens to a bird with few predators. -- JSBillings 14:40, 31 October 2007 (UTC)

(After edit conflict) A general instinctive fear of being killed and eaten by a creature much larger than themselves? The street pigeons seem to mostly tolerate humans, seeing them as something to simply move out of the way of - as they understand from experience that the majority of the large bipeds of the concrete forest pay them little attention and mean them no particular harm. They only seem to become agitated and take flight (around here, at least) if a human is getting too close, actively following them around, trying to trap them up against a wall, or running/walking towards them at speed - all of which the bird may (rightly?) interpret as hostile acts. --Kurt Shaped Box 14:43, 31 October 2007 (UTC)

Great answers. Thanks all. --Richardrj ^{talk email} 14:53, 31 October 2007 (UTC)

(another edit conflict) I think the 'rule' is probably more general than "man should be avoided" - something more along the lines of "if it's bigger than you and coming towards you, it should be avoided". Birds that tended to fly away when approached by something bigger than them would have an evolutionary advantage over those who hung around because that something may be a predator. Even if it's not a predator, it's extremely unlikely that it would be something that would provide the bird with some advantage over its fraidy-cat brethren who didn't stick around long enough to find out, so the wait-and-see trait would be disadvantageous and would die out. The impulse is still there because it's still advantageous, even amongst city-dwelling birds, to get out of the way of bigger things (imagine how odd would be if birds all wandered around on crowded streets, or didn't bat an eyelid if they were standing in the road and a car approached).

In fact, not all birds take flight as soon as they're approached by a human. Before it was banned, holding a handful of seed in Trafalgar Square was guaranteed to result in you being mobbed by pigeons. — Matt Eason ^{(Talk &#149; Contribs)} 14:58, 31 October 2007 (UTC)

Yes, they're afraid because instinct tells them anything that gets close to them is probably trying to eat them! Although they are used to humans, they are still preyed upon by cats etc. Feral Pigeons are sufficiently tame to approach a human if they have food and some birds can be tamed so that they are not afraid of humans, my two pet budgies will run up to me and climb onto my hand if they are on the floor and I hold my hand out. It's just a case of convincing the bird that you are not going to harm it which takes time and perseverence. At the end of the day, one of the most basic instincts of all animals is to survive which means avoiding anything that is likely to be dangerous.GaryReggae 15:01, 31 October 2007 (UTC)

If human bodies had thick fur like other mammals, do you think we would still wear clothes?

She didn't. Rockpocket 20:25, 31 October 2007 (UTC)

Do you? 64.236.121.129 19:16, 31 October 2007 (UTC)

Hmm, that's a fun question. It depends where our sense of modesty comes from. I would imagine without the invention of clothing and the ability to cover up, there would be no way for embarrassment of genitals to come about. However, clothing also provides an additional sense of style and individuality. So maybe, just being human, we'd wear some sort of clothing anyway -- MacAddct1984 19:47, 31 October 2007 (UTC)

Individuality could be expressed by styling and coloring the fur, but I think clothing would still have been invented. Much of it provides a lot of utility beyond keeping warm. Lab workers, for example, would probably still wear some variation on a lab coat. Police officers would still wear Kevlar vests. I'm no expert, but it seems like if our current attitudes towards clothing evolved from the need to cover up in cold weather it wouldn't be surprising if other uses for clothed eventually evolved into similar attitudes. 69.95.50.15 20:18, 31 October 2007 (UTC)

Also where would you put your wallet if your a man? Certainly i'd still wear clothes, gotta have a place for my phone, keys, wallet and iPod...You can see why mugging is so popular! The above stuff is right too, clothes are cultural-identity too, they are also a sub-culture thing. Goths, punk rockers, skaters, sports-addicts, 'chavs', horse & hound types etc. A lot of clothes (and styles) seem to have started their life as work-based clothing and/or developed to become fashion/general wear. Jeans were work-clothes (still are), Cargo pants, three-piece suit (though Adam Hart Davis suggests it was an attempt by the British to reduce the love of French clothing in the Stuart period), sports-wear is obviously often derived from sport-use clothing. Obviously work-wise these things are not just to cover modesty but as a form of protection/security/uniformity too ny156uk 23:38, 31 October 2007 (UTC)

How much sugar does the average kid/adult consume on Halloween?

^topic 64.236.121.129 19:23, 31 October 2007 (UTC)

Can you have an average kid or adult? ΦΙΛ Κ 21:09, 31 October 2007 (UTC)

Well you would expect that in any 'holiday' season people will allow themselves more treats, so possibly some like say three times as much as the 'average' sugar intake on any other day. This article (http://www.sys-con.com/read/451581.htm) is basically utter garbage but it does mention halloween and sugar intake. ny156uk 23:33, 31 October 2007 (UTC)

Cyanide and suicide

Is suicide via ingestion of cyanide, as seen in James Bond movies, fact or fiction? Babalonia 3. —Preceding unsigned comment added by 66.74.109.242 (talk) 20:41, 31 October 2007 (UTC)

As can readily be found in our article on cyanide, it can quite easily be used as a poison. Adolf Hitler, among others, used it as such. — Lomn 20:57, 31 October 2007 (UTC)

When you say "as seen in James Bond movies" do you mean ingestion of cyanide causing death in seconds? Sifaka ^talk 22:52, 31 October 2007 (UTC)

I thought Hitler died from shooting himself (though his wife and dog were killed by cyanide pills). — Daniel 03:18, 1 November 2007 (UTC)

Exercising, Muscle Burn and Calories

Upon reading over several articles (such as muscle and exercising ), I’ve got a few questions relating to “muscle burn” after a rigorous workout. Assume that one runs a mile on a treadmill. Most treadmills indicate calories burned over the duration of the run. Further assume that, according to the treadmill, 200 calories are burned (let’s pretend this number is accurate). If the runner has muscle burn from the rigorous run, does he/she actually burn more calories than the 200 indicated by the treadmill? I would assume so, as the body is ‘recovering’ from the workout, and thus will burn additional calories post-run.

Thoughts? Rangermike 21:25, 31 October 2007 (UTC)

See Lactic acid and Delayed onset muscle soreness, if you are referring to the fatigue and soreness one feels in one's muscles during and after workouts.

This is out of my field, but the body is burning calories with everything you do, say, or feel, but nothing burns as quickly from homeostasis as physical motion. For a physicist's example, say you were sick, and you had a fever of one degree celsius. At a weight of about 100kg, you would burn 10^5 calories = 100 kcal (kilocalories or kcal are the actual unit of measure when people refer to "calories". One calorie properly refers to the heat necessary to raise the temperature of 1 gram of water by 1 degree celsius). Keep in mind, this fever builds up over several hours, whereas you can burn that much in a 30 minute workout. SamuelRiv 03:28, 1 November 2007 (UTC)

Gravitational pull of the moon

Hi,
I've heard that there is no instrument on the earth which can measure the gravitational pull of the moon (apart from the obvious affects of the tides). Is this true? --124.181.69.55 21:35, 31 October 2007 (UTC)

Let's see here.... The Earth will pull on a 1 kg mass with a force of 9.8 newtons. Using an Earth-Moon distance of 380 000 km, the Moon overhead would tug on the same mass with a force of about 34 micronewtons. So the apparent weight of an object due to the moon's motion over the course of a full lunar orbit will appear to vary cyclically over about 70 parts per million. That's not a huge amount, but it's certainly measurable. Particularly if one monitored a very stable, very precise balance over the course of several lunar orbits, I would expect the effect of the Moon's pull to stand out as a periodic oscillation. A very quick Google search for microgram balances finds this one, which will set you back about $7000, and which will measure masses up to 5 grams with a resolution of 2 micrograms (about 0.4 parts per million). Can someone check my numbers? TenOfAllTrades(talk) 22:05, 31 October 2007 (UTC)

I get 7 ppm from your numbers (2 * 34e-6 / 9.8) — Lomn 22:25, 31 October 2007 (UTC)

In theory, there's no reason you can't. In practice, it may be the case that tolerances don't allow us to (I'm not sure). Just for reference, though, here's what you're dealing with. Gravitation is a function of mass over distance squared. For the Earth, we'll say that it's M/R², where M is the mass of the Earth and R is the radius of the Earth, and we'll normalize that resulting number to 1. The Moon, on the other hand, masses roughly 1/80 Earth, and never gets closer (to the surface) than about 56R at perigee. Substituting, we expect that the Moon causes a discrepancy over a no-Moon Earth of 1/(80*56*56) -- that is, 4*10^-6 or 0.0004%. Now, in practice, that discrepancy can be roughly doubled -- the difference between the Moon directly overhead and directly underfoot (noting that the move from 56 to 58 Earth radii is pretty minor at this point). So in total, to detect the influence of the Moon's gravity on Earth-surface objects, you need accuracy to six digits, or one one-hundred-thousandth of the object. (ec) I notice that I'm an order of magnitude off Ten's answer. Time to double-check. — Lomn 22:13, 31 October 2007 (UTC)

I will note, however, that you're monitoring a periodic variation of [whatever the correct magnitude, 7 or 70 ppm] over a day, not a lunar orbit (month). Monitoring over the course of a month could be used to confirm the roughly 25% variation in the daily cycle resulting from the eccentricity of the Moon's orbit. — Lomn 22:18, 31 October 2007 (UTC)

Oops, right. The Earth rotates once a day, doesn't it? Dang. Double oops; you're also right about the 7 ppm (not 70). I'm going to have to turn in my physics license. TenOfAllTrades(talk) 23:02, 31 October 2007 (UTC)

LIGO has to compensate for lunar tides, so there is an example of an active experimental instrument that is sensitive to the moon's gravity. Dragons flight 23:43, 31 October 2007 (UTC)

They did it on an episode of mythbusters. They used an extremely powerful accelerometer to measure if the anti-gravidy contraptions had any effect whatsoever (they didn't). They breifly mentioned the accelerometer measuring the tidal forces from the moon and showed the graph it made. — Daniel 02:01, 1 November 2007 (UTC)

You may be confusing an important law in Special Relativity, which states that a person in a closed space can never tell whether he is being accelerated due to external gravity or some other outside force (such as a rocket). See the article for details. You may also be thinking of the Cavendish experiment, in which the gravitational force of the moon, the planets, and the Earth were all simultaneously measured by measuring the gravitational constant G, which combined with Newtonian orbit theory gives everything you could possibly want about gravitational forces in the solar system. SamuelRiv 03:27, 1 November 2007 (UTC)

oxidizers

are they flamible without fuel?

Various ether peroxides, like Acetone peroxide, Diethyl ether peroxide, and Tetrahydrofuran peroxide spontaneously explode when disturbed. Lab accidents involving such peroxides formed when a bottle of ether is exposed to light, oxygen, or catalytic metals and then subsequently ignored for a long time happen every once in a while. Sifaka ^talk 23:15, 31 October 2007 (UTC)

Thinking more about this, I bet some oxidizing agents with more complex chemical structures could react with themselves or other molecules of the oxidizer. There are probably also some nasty chemicals which have the potential to react under a variety of storage conditions without deliberately added fuel. Sifaka ^talk 23:28, 31 October 2007 (UTC)

oxidation

is mn203 a good pyrotechnic oxidizer? —Preceding unsigned comment added by 216.103.183.127 (talk) 21:59, 31 October 2007 (UTC)

I'm not getting any hits on google for manganese (III) oxide (also called manganese sesquioxide) being used as a pyrotechnic oxidizer. Safety precautions for the compound as listed in the sigma aldritch catalog (source) list it as an irritant to eyes, respiratory system and skin so I doubt people would appreciate it being scattered about by pyrotechnic displays where it could be inhaled. Among the applicable safety phrases it says don't add water to it. Of important note is that sigma didn't list it as an oxidizer, so I am leaning towards doubting its efficacy as an oxidizer at this point (I need to research around a little more). Many other manganese compounds appear to be fairly strong oxidizers including Manganese(III) acetate. Perhaps you meant to ask about one of them instead? Try looking at the manganese page. Sifaka ^talk 23:58, 31 October 2007 (UTC)

Tased across the spine

Can a person be paralyzed if the electrodes are opposite the spinal cord? I recently saw a video of someone getting tased in the back (the flying wires kind, not the little zapper kind) and it made me wonder --ffroth 22:14, 31 October 2007 (UTC)

See Taser for details. The weapon uses a shaped electric current to disrupt nerve function, I suppose in a process similar to a localized seizure. Unless structural damage occurs to nerve fibres or bone, the current itself shouldn't produce permanent effects. The brain and spinal cord both have a certain degree of plasticity (ability to change - i.e. learning) that is believed to depend on the intensity and duration of electric currents. See Electroconvulsive Therapy for information on the effects of high-intensity electric currents on the brain. Permanent effects to the spinal cord could possibly be similar, but would only affect memories stored in the spine, namely "muscle memory". —Preceding unsigned comment added by SamuelRiv (talk • contribs) 03:38, 1 November 2007 (UTC)

secret service mobiles

Just curious about how this locking down on mobile signal works and how do the mobiles that are manufactured against it work.88.203.105.48 22:42, 31 October 2007 (UTC)

Rising Sea Levels and the Effect this Will Have on the Mediterranean Ocean

Given that the Med is regarded (more or less)as a tideless sea and that this is largely due to the influence of the Straits of Gibraltar which constrict the tidal bulge caused by the gravitational pull of the sun and/or the moon. At what point, if at all, or to what degree, in the earths future, will the Med see a real tidal effect once the seas have risen enough to overcome the resistance of the Straits of Gibraltar? Much of the Med coastline is at or very near sea level because there has never been any need to make allowances for tidal fluctuations. —Preceding unsigned comment added by 79.68.42.88 (talk) 23:08, 31 October 2007 (UTC)

Well much of all society is near the sea/lakes because historically we settled near places with ready access to water. The med problem is interesting. I expect it would require an extremely large increased. As the article (Strait of Gibraltar) notes water depth ranges from 300m to 900m, the opening is some 8 miles wide - having said this the end of the article has a bit on the 'need for a dam' so might be worth having a look at that link (http://www.agu.org/sci_soc/eosrjohnson.html) ny156uk 23:28, 31 October 2007 (UTC)

facial hair

Why do males have facial hair? Why don't females? —Preceding unsigned comment added by 68.231.151.161 (talk) 23:45, 31 October 2007 (UTC)

Vestigial trait. Doesn't serve any meaningful purpose unless you are white, it can sort of protect the face from UV radiation, but melanin (dark skin) does a much better job of that, and protects everywhere. So in other words, it's useless from a utilitarian point of view, but has cultural and social significance. Malamockq 01:24, 1 November 2007 (UTC)

Finite from Infinite

Today's science dictates that not only is a theoretical construct of infinite density, energy, and size possible; it's actually how the universe started. How does a finite universe come from something that is infinite? —Preceding unsigned comment added by Sappysap (talk • contribs) 23:55, 31 October 2007 (UTC)

Firstly, there is no accepted theory suggesting the Universe is finite. While the observable universe is quite finite, the actual universe is possibly infinite in extent and mass. Further, physics does not posit that the universe began in a state of infinte density. It actually doesn't posit anything accepted about where it came from, as the Big bang theory only deals with what happened after (very soon after, though) the universe started existing. Someguy1221 00:27, 1 November 2007 (UTC)

Thirdly one way to look at it is fintite mass divided by zero size gives infinite denisity. Graeme Bartlett 00:30, 1 November 2007 (UTC)

I'm a huge fan of all of you guys who answer these questions...Someguy1221, Rockpocket, SteveBaker, Dragon's Flight and the whole crew. Please have infinite patience with me while I ask the following: How can the universe have infinite mass without infinite density? How can it have infinite extent and continue to expand? Sappysap 01:07, 1 November 2007 (UTC)

As for the first, I'm still trying to get my head around it, but for the second, imagine a piece of elastic, infinitely long, with small knots tied at regular intervals. Now imagine the elastic being stretched - you'll see the knots moving apart, even though you can't see the "ends" moving apart. Confusing Manifestation 02:00, 1 November 2007 (UTC)

To answer how the universe can have infinite mass without infinite density, all you have to do is think of numbers. There are infinitely many integers, as I'm sure you're well aware. There are also infinitely many numbers inbetween every two integers. And so, you manage to have a system of infinitely many numbers containing an infinite number of integers yet not every number is an integer. Actually, as you might suspect from there being infinitely many numbers between two integers, and only finitely many integers between any two numbers, each integer is like a tiny island in the sea of infinity. So, in conclusion, your infinitely many integers occupy an infinitely small portion of the number line. So I think you can see from this how you can have, in an infinitely large universe, infinitely many masses without filling up every possible space with a particle. As for having infinite extent, I haven't quite figured or accepted that one yet, except to say that lots of astronomers believe this (it is in part just a conclusion from the evidence that the Universe has no center or edge). Someguy1221 02:33, 1 November 2007 (UTC)

The universe has infinite mass if and only if it has infinite volume. Obviously everything around us has finite density, but if you allow yourself to collect more and more of it without limit, then ultimately you arrive at an infinite amount occupying an infinite volume. It is unknown whether the universe is truly infinite in extent, but it appears likely that it must be very much larger than the observable universe we can see. Dragons flight 03:26, 1 November 2007 (UTC)

None of the above physical quantities are or ever were truly infinite. The widespread modern cosmologies (that is, those based on Einstein’s general relativity, which came out about 90 years ago) all involve a universe that is finite in size and energy (or mass). And I’m talking about the entire universe, not just the visible universe. It isn’t really accurate to say that the density of the universe was infinite at the exact moment of the big bang, either. Singularities in a physical theory generally indicate a point at which the physical model breaks down, not that there really is an infinite physical quantity at that point. In this case, physics within the Planck epoch are poorly understood, but it appears that it is meaningless to talk about distances less than one Planck length, which is a finite distance, or time intervals shorter than the Planck time, which is also finite. So it isn’t meaningful to talk about energy densities greater than the (finite) total energy of the universe divided by the volume of a sphere whose diameter is a Planck length, or meaningful to talk about the exact instant of the big bang. MrRedact 02:46, 1 November 2007 (UTC)

I'm not sure what the initial question refers to, specifically. There are indeed important resolutions of infinite results in Quantum Field Theory, which I might be able to expand upon if a detailed question is posted, but all "physical" results must be finite by definition. Unresolved singularities (infinite results) signify a failure of a theory, not a physical reality. Cosmology works a little differently, but even then most cosmologies I know of do not accept any premise of infinity except perhaps in the context of a ground state (see vacuum). SamuelRiv 03:45, 1 November 2007 (UTC)

You are confused. General relativity permits solutions that are either infinite or finite in extent, and so is essentially agnostic on the issue. (See for example: Friedmann-Lemaître-Robertson-Walker metric, which permits different homogeneous and isotropic solutions discriminated primarily by whether the universe is finite or not.) For the universe to be finite, it must have a global curvature such that a person traveling in what appears to him to be a straight line will eventually come back to places he has been before. Such a curvature is possible, but not required, in GR. Your description of the Planck quantities is also problematic. It is not that there couldn't theoretically be smaller lengths, times, etc., but rather that describing events at those scales intrinsically requires both an unified understanding of gravity and quantum mechanics. In other words it requires an as yet ill-defined theory of quantum gravity. So, it is meaningless primarily in the sense that science as it now exists is not able to provide it meaning. Future theories may yet shine a light on events in and before the Planck epoch. Dragons flight 04:09, 1 November 2007 (UTC)

November 1

What Are Some Things All Things On Earth Have In Common That Are Living Or Non-Living?

I wonder, what are some things all things on Earth have in common that are living or non-living? —Preceding unsigned comment added by 208.103.143.9 (talk) 03:07, 1 November 2007 (UTC)

Please clarify your question. Everything is living or non-living. — Daniel 03:15, 1 November 2007 (UTC)

They're all made up of atoms? -- MacAddct  1984 ^{(talk &#149; contribs)} 03:19, 1 November 2007 (UTC)

Not everything is made up of atoms. Evidence_of_evolution#Evidence_from_comparative_physiology_and_biochemistry lists many things that living things mostly have in common. As for non-living things, their only binding similarity is that they aren't living. Someguy1221 03:21, 1 November 2007 (UTC)

They're all made of matter and/or energy, they're all affected by the laws of physics, and they all hate getting circus peanuts on Halloween.  ;-) -- HiEv 04:07, 1 November 2007 (UTC)

Contradiction in mass-to-energy equivalence?

I'm new at Wikipedia editing and whatnot, so I wasn't sure where I should put this where it would be noticed:

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The article "Antimatter Weapon" states:

Quantities measured in grams or even kilograms would be required to achieve destructive effect comparable with conventional nuclear weapons; one gram of antimatter annihilating with one gram of matter produces 180 terajoules, the equivalent of 43 kilotons of TNT.

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The article "TNT equivalent" states:

By E = mc^2, when 1 kilogram of antimatter annihilates with 1 kilogram of matter the reaction produces 1.8×10^17 J, which is equal to 42.96 Mt.

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While I could just do the basic equation (mass*c^2, and convert joules to TNT equivalence), I didn't want to make an assumption without consulting anyone else first lest I made a mathematical error or overlooked some other factor in the calculation. —Preceding unsigned comment added by 24.65.12.157 (talk) 04:44, 1 November 2007 (UTC)

1 kilogram is 1000 grams; 1 Mt (megaton) is 1000 kilotons. Is that what you are confused about, or is there something else? Dragons flight 04:48, 1 November 2007 (UTC)

Ugh. I missed the "one gram" versus "1 kilogram" part. Well, we all make mistakes. C'est la Vie.