Wikipedia:Reference desk/Archives/Science/2007 October 26

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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)