Wikipedia:Reference desk/Archives/Science/2007 September 11

= September 11 =

Lift/Drag/Thrust/Weight Diagram
I recall from early physics classes that the classic simplified version of lift-drag-thrust-weight for aircraft mechanics is the first thing that pilots learn about. Yet, I can't find an image or diagram of this model anywhere on Wikipedia! I've found some similar versions from a few other websites. I was about to expend some effort to make a nice SVG version similar to this image. Any suggestions or prior work? I found this, but it doesn't show the plane (so it's not very useful for lay-person usage). Nimur 02:13, 11 September 2007 (UTC)
 * You may also wish to post this at Wikipedia talk:WikiProject Aviation. -- Flyguy649 talk contribs 02:39, 11 September 2007 (UTC)


 * If you're looking for a line drawing of an aircraft, there's a whole pile of them on Commons: commons:Category:Aircraft line drawings. Perhaps you could slap the lift/drag/thrust/weight arrows on to one of those? TenOfAllTrades(talk) 02:43, 11 September 2007 (UTC)

Holes in Cheese
This is a serious question; I am curious to know why some cheese has holes and others don't. I would really like a detialed answer with "chemistry", or the chemistry of what happens. Thanks! Phgao 07:21, 11 September 2007 (UTC)
 * From the article on swiss cheese: "In a late stage of cheese production, the Propionibacter consumes the lactic acid excreted by the other bacteria, and releases carbon dioxide gas, which slowly forms the bubbles that develop the [holes] ." --π!  08:04, 11 September 2007 (UTC)


 * So I would take it that this bacteria produces the holes in all holed cheese? I think I'll do a bit more reseach, and that article http://en.wikipedia.org/wiki/Propionibacter_shermani looks like it could do with some work. Phgao 09:34, 11 September 2007 (UTC)

Illness causing hair loss
When I look up "hair loss" in Wikipedia, it brings me straight to "baldness". Is it true that extreme illness or stress can cause hair to fall out? Is there a term for this? Are there any particular diseases for which this is considered a common symptom? (Of course, excluding hair loss as a result of cancer treatment.) --π!  08:01, 11 September 2007 (UTC)


 * Alopecia areata, totalis and universalis? Capuchin 08:04, 11 September 2007 (UTC)


 * I meant, something that's not usually considered simply "baldness". Losing hair as a side effect as another disorder, not specifically a hair-loss disorder.  --π!  08:09, 11 September 2007 (UTC)


 * Sorry, I don't understand, you're looking for "baldness" that is not "baldness"? Capuchin 08:14, 11 September 2007 (UTC)


 * You might want to use some of these symptom search engines and see if they come up with anything. I can't as i'm at work: Capuchin 08:20, 11 September 2007 (UTC)


 * Aha, WebMD had some good answers! Hair loss can be a symptom of: "mental or physical stress, such as recent surgery, illness, or high fever", "poor nutrition, especially lack of protein or iron in the diet", ringworm of the scalp, thyroid disorders, lupus, syphilis, cancer, and hormonal changes. --π!  10:37, 12 September 2007 (UTC)


 * And I didn't notice it in the baldness article before, but the scientific name for hair loss caused by stress is telogen effluvium. --π! 10:43, 12 September 2007 (UTC)


 * Re Capuchin - I assume Pi is talking about things that generally cause temporary hair loss rather than permanent baldness, for example chemotherapy typically leads to temporary baldness, but the hair usually grows back once the treatment stops. --jjron 08:23, 11 September 2007 (UTC)


 * From alopecia areata: "About 50% of patients' hair will regrow in one year without any treatment." Capuchin 08:34, 11 September 2007 (UTC)


 * I saw hair loss with lupus once.Polypipe Wrangler 11:30, 12 September 2007 (UTC)


 * (Standard medical disclaimer: This is not medical advice. For any medical condition you should see a licensed medical professional.)  There is a list of 343 causes of hair loss at Wrong Diagnosis, but even with such a complete list I see that they didn't include Mercury poisoning.  152.16.59.190 05:46, 13 September 2007 (UTC)

Incidence of brain tumours
Is the incidence of brain tumours in the developed world increasing, and if so, what theories have been advanced to explain this? Our article mentions increasing incidence of brain tumours in children, but doesn't say anything about adults. --Richardrj talkemail 08:18, 11 September 2007 (UTC)
 * There are two possible reasons: either 1) our capacity to diagnosis brain tumors is increasing and we're now picking up more tumors than we were previously able to, or 2) the actual incidence of brain tumors is increasing. The fact that humans are living longer and that age predisposes to cancer supports the later argument. An argument for the former is that recent advances have allowed for improved diagnosis (eg, MRI and CT) and classification (eg, widening criteria necessary for diagnosis) of tumors, including brain tumors. This article expands on that argument, noting that the incidence of some "not otherwise specified" primary brain tumors have gone down while the number of more specific diagnoses for primary brain tumors has increased. There are plenty of hypotheses out there that specific chemicals are responsible for an actual rise in brain tumor incidence, but I don't know of any epidemiological studies that have made any good conclusive arguments (then again, I haven't really looked). --David Iberri (talk) 20:08, 11 September 2007 (UTC)


 * I agree. Everyone dies of something.  If we wipe out a disease - or make cars safer or have better law enforcement to reduce the murder rate - then INEVITABLY something else increases in prevelance because in the end the total of the probabilities of dying from all possible causes adds up to 100%.  Cure cancer and everything else increases in probability.  A better measure would be the average age of people with the disease.  If that's decreasing then you have a real problem.  If it's increasing then we probably shouldn't worry. SteveBaker 14:47, 12 September 2007 (UTC)
 * So, what is the average age of people with brain tumours? And is it increasing or decreasing?  There must be statistics on this somewhere. --Richardrj talkemail 21:12, 12 September 2007 (UTC)

Birthrate skewed towards males?
This newspaper article suggets that even in industrial countries birthrate is skewed towards male offspring. I would have thought it would be 50/50? Why is this the case? http://news.ninemsn.com.au/article.aspx?id=294933 Quote, "the ratio in industrialised countries is 107 to 104 boys for every 100 girls." Phgao 10:49, 11 September 2007 (UTC)


 * Males die younger. I think nature strives for somewhere around 50:50 after "corrections" (probably 50:50 at childbearing age or something). Capuchin 10:52, 11 September 2007 (UTC)
 * see Sex ratio --Spoon! 13:15, 11 September 2007 (UTC)


 * One reason I've heard given is that in a society where children are at high risk of dying, it makes more sense to produce lots of females, which boosts the birth rate at the cost of genetic diversity (few males producing many children narrows the gene pool), while when most children survive to reproduce, there is no need to produce more than about 1 child per person (2 per couple, hence the classic 2.4 children concept). As a result, this society needs fewer females and more males, which will then increase the gene pool and reduce the incidence of genetic disorders. Incidentally, one cause of the high male-female ratio is that in both India and China, the largest centres of population in the world, boys are more highly regarded than girls and, with China's one child policy especially, families may choose to selectively abort female babies or not report the birth to the authorities, thus allowing them to try again for a boy. Laïka  13:26, 11 September 2007 (UTC)
 * looking at it from the other direction, "female" sperm carry an x chromosome, "male" sperm carry a y chromosome. The y chromosome is a lot smaller than the x chromosome, and the sperm is such a stripped down little hot rod that it makes a difference in its speed, so that "male" chromosomes have a better chance of being the first at the finish line, i.e. the ovum. Gzuckier 16:04, 11 September 2007 (UTC)
 * Several obvious problems with that including that evolution wouldn't have allowed the such a travesty of an imbalance to have survived so long, and also it doesn't account for why this only applies to to certain countries, especially seeing as most are skewed towards females, notably Russia which had, and apparently still has, a massive imbalance towards females caused supposedly by food shortages. Combined with the reasoning above and that, females intrinsically seem to be smaller and naturally less active than their male counterparts, and more likely to survive in a food shortage. ΦΙΛ Κ  18:28, 11 September 2007 (UTC)

I wish I had a reference for this, but I have heard this discussed on more than one radio show (NPR, not Rush Limbaugh), and if I remember correctly there was something about the pH of the vagina and uterus being governed by stress hormones, which apparently can have some effect on the survival rate of x-carrying and y-carrying chromosomes. (some more about that here, try googling "sperm gender pH acidity selection" and you might find more. -- SB_Johnny | PA! 19:44, 11 September 2007 (UTC)


 * Thanks for the responses! I think there should be a distinction made; yes it is true that in china the male/female ratio is skewed, but that doesn't explain why the *birth* male/female ratio is slightly skewed, as is said in the article above. That is to say the birthrate even in industrialised nations is around 105boys per 100girls, even though this even outs as the population ages as males die younger. What User:Philc_0780 said could be it, but I'm still not sure. Phgao 03:56, 12 September 2007 (UTC)

Relative size of the sun
If the Earth was the size of a pinhead, how big and how far away would the Sun be? I was thinking about this and realise I have no idea - I mean I know it would be big, but what, as big as a fridge? A house? A country? 195.60.20.81 16:01, 11 September 2007 (UTC)
 * You can get the actual sizes by reading our encyclopedia articles: the Sun has a diameter of 1.392×109 m and is 1.496×1011 m from earth. The Earth has a radius of 6,372.797 km. In your model, the earth is a pinhead (estimate about 1 mm for convenience), so you just need to scale all the measurements to match. Actually, the Sun article even tells you explicitly that its diameter is equivalent to 109 earth diameters, so that's 109 pinheads without having to do any math at all, or 109 mm (which is about 11 cm). DMacks 16:51, 11 September 2007 (UTC)


 * I found this question interesting. Thanks.  So, you are saying that ... if the Earth were the size of a pinhead, then the Sun would be the size of 109 pinheads ... correct?  And what about the distance?  Measured in pinheads, how far is the distance from the Sun to the Earth?  Also, can you give a reference example, such at the question originally posed?  That is ... can you please fill in the two blanks with the names of a common and recognizable everyday household object: If the Earth were the size of a pinhead, the Sun would be the size of a __________ ... and the distance of the Earth to the Sun would be the size of a __________.  Thank you.  (Joseph A. Spadaro 17:03, 11 September 2007 (UTC))


 * For the distance, the sun is 1.49e11/6.37e6 or 23478 earth diameters away. If the earth was 1 mm, that would be 23478 mm = 23.4 m, or about 25 yards.128.163.170.17 17:26, 11 September 2007 (UTC)


 * So that's a pinhead and a grapefruit and either end of my standard swimming pool.--Shantavira|feed me 18:34, 11 September 2007 (UTC)


 * Make that a football, because I just bothered to actually measure a pinhead and it was 2.5 mm wide. It's rather common to misjudge the size of small round objects. DirkvdM 18:51, 11 September 2007 (UTC)
 * Yeah, depends what kind of pins you use for reference (I hate using "normal" objects for reference size when the object's variation is so relatively large). The pins I usually use have a head that's just the end of the wire pressed down (like the head of a nail), barely wider than the wire itself. Very much smaller than the easier-to-handle (and admitedly better for building a scale-model:) than the oversized plastic heads as in Image:2006_01020005.JPG. DMacks 20:04, 11 September 2007 (UTC)
 * 128., I believe you mixed up radius and diameter. If the Earth was 1mm in diameter, the sun would be 11.7 m away.  --Sean 23:27, 11 September 2007 (UTC)


 * You might also be interested in Solar system model. --Sean 23:19, 11 September 2007 (UTC)


 * We need to add pinhead to our list of unusual units of measurement.--Shantavira|feed me 09:27, 12 September 2007 (UTC)


 * In which case we might also add the distance between the tips of my thumb and little finger when I spread my hand, which is 20 cm (21 cm if I overstretch it). Very handy to know when I don't have a measuring tape at hand. I did add the 'Balkenende' as a unit of income. DirkvdM 19:30, 13 September 2007 (UTC)

Determine the voltage/current for random LEDs
Hi all,

If I were to get a big bag of random LEDs (like those here with big ones, little ones, rectangular ones etc, how could I determine the correct voltage and current to use them with? Can I just go by the color, like in the chart at the bottom here &mdash; is that the same for all shapes and sizes? Can I use my multimeter to work it out?

Thanks! -Sam. 17:56, 11 September 2007 (UTC)


 * Our article on LEDs contains a table of voltages for different colours of LED - all LED's of the same colour take the same voltage range. You should properly connect up the LED with a current limiting resistor - but the amount of current required for a particular LED depends on the nature of how it was manufactured - and how much light it's going to put out - and to know that you need a data sheet. You could hook each one up in turn to a variable resistor and slowly change the voltage until the LED lights with an acceptable brightness (or blows up!). That would let you know how big a resistor to wire up to each type. SteveBaker 19:20, 11 September 2007 (UTC)


 * And, assuming your series resistor is (or can be) big enough, the voltage you start with doesn't matter so much. Just use 3v or 5v or whatever you've got handy.  When you've chosen a resistance that seems to give you the right brightness, you'll have empirically determined both the LED's current draw and voltage drop. —Steve Summit (talk) 00:38, 12 September 2007 (UTC)


 * Connecting it to e.g. a 20mA current source would also work, if you have one handy. Then you can slowly crank up the current until it's bright enough for your purpose. --antilivedT 20:12, 11 September 2007 (UTC)


 * Indeed. But if you don't know what a current source is and how it differs from the more usual constant-voltage power supply (i.e. voltage source), definitely go with Other Steve's variable resistor suggestion instead. —Steve Summit (talk) 00:30, 12 September 2007 (UTC)

FYI: 20 mA is too much for some LEDs; I'd start with 5 mA instead. Also, a very few LEDs contain internal resistors or current-limiting chips; these will give surprising results as you vary the voltage/external resistor, but if you know these variants exist, you'll be able to figure out what's going on if you see one. Finally, while diode voltage and color are intimately related for monochromatic LEDs ('cause it produces photons with x electron volts of energy), the operating voltage for "White" LEDs varies depending on which technology they use to produce the "white" light; today, most are actually blue LEDs with phosphors/scintillators that convert some of the blue to yellow.

Atlant 14:32, 12 September 2007 (UTC)


 * It really depends on the size of the LED. Most of the 3+mm LED's that I get to play with will work happily with 20mA, but definitely not the SMD ones. --antilivedT 10:21, 13 September 2007 (UTC)

One more thing. I'm pretty sure you always want to use a series, current-limiting resistor. That is, you would never ask for an LED's "voltage rating", and then use a power supply of exactly that voltage, without a resistor at all.

One reason is simply that the voltage is so low. The voltage drop across a forward-biased P-N junction in an ordinary silicon diode is 0.6v. I'm pretty sure the voltage drops in LED's are comparable. But that's considerably lower than the power supply voltage in any typical electronic circuit. (Part of the reason is that the power supply voltage in any typical electronic circuit has to be substantially higher than 0.6v, and in fact higher than 2&times;0.6v or 3&times;0.6v, precisely so that it can overcome the voltage drops across the P-N junctions in the circuit's various other diodes and transistors.)

But more importantly: a diode is most certainly not an ohmic device; that is, it does not obey Ohm's law. If I were to put a forward-biased diode (light emitting or otherwise) across an 0.6 volt power supply, how much current would flow? An almost infinite amount, actually. Other than the 0.6 volt drop across it, a forward-biased diode looks a lot like a dead short; in fact in most cases (e.g. rectification) that's it's job.

So you want a resistor in the circuit to limit the current, and once there's a resistor in there limiting the current the voltage is going to have to be higher than the diode's voltage drop so that it can also accommodate the voltage drop across the resistor, and once you've got a voltage drop across the resistor you might as well adjust the resistor's value until you end up with a total voltage that matches the one supplying the circuit you're driving the LED with.

It's for this reason that the primary electrical specification for an LED is the current, I think (that is, the value you want your current-limiting resistor to limit the current to), with the "voltage" buried in the fine print, because in practice you hardly care about it at all. —Steve Summit (talk) 04:46, 14 September 2007 (UTC)

What's this called?
(I was going to say "what's the matter with my mind?", but it seems too melodramatic). I've been enjoying contributing here over the past several days, and it really strikes me how my mind is what my wife calls a "steel trap" for abstract things like the scientific names of organisms and random trivia, but I can't for the life of me remember people's names without hearing them or reading them repeatedly. This applies equally to people I meet, actors, etc. (but not, oddly enough, to politicians). I know it's a form of selective memory, but it's really embarrassing sometimes, and I know it's not unique to me. Is there a name for this problem? -- SB_Johnny | PA! 19:51, 11 September 2007 (UTC)
 * Autism is often characterized by highly developed mental faculties with very poor social skills (such as proper behavior around people, and inability to use names, etc). It doesn't sound like you're there, but my understanding of psychology is that there's a very broad spectrum, rather than precise categories.  Nimur 01:25, 12 September 2007 (UTC)
 * Ouch! I can relate only too well to you, Johnny, but I'd shrink from any thought that I was even minimally autistic.  (People who know me may well disagree.)  I know exactly what you're experiencing.  I have a mind full of a bazillion bits of (mostly worthless) information, but putting names to faces - and even recognising faces I've met before - is becoming harder and harder.  It's very embarrassing, and I'm aware I've unconsciously developed ways of avoiding revealing that I don't remember the name of the person I'm with.  I always assumed it's a part of the ageing process, and I've more than once wondered if I'm meandering slowly but inexorably into Alzheimer's territory.  --  JackofOz 01:37, 12 September 2007 (UTC)


 * I can also relate very well. My wife has an irritatingly reliable memory when it comes to names, faces, what people have given or gotten what gifts and what people wore at events even in the distant past. On the other hand, I have an extremely hard time with it. I also wondered what the matter was until it struck me: I didn't really care all that much. I can recite baseball stats and comic book lore and an insane amount of science type stuff. Why?  I find it interesting. To be blunt, I just don't care for most people all that much; I don't *hate* people, I just find most folks tedious or irritating. Uh, present company excepted, of course. I think my issue is that I unconsciously decide not to expend the energy to memorize a name/face combo because I unconsciously don't care to. By that same token, I can remember a great many details about the friends I do have, probably because I actually pay attention when they're talking.... Matt Deres 02:13, 12 September 2007 (UTC)


 * "Me too." I think part of it is that I remember data better if they're part of a pattern, and the names/faces of random people aren't.  Every time I start a new job, someone leads me around and shows me all the people there, and maybe they remember me but for me it's a dead loss: they don't individually attach to anything yet.  —Tamfang 07:21, 12 September 2007 (UTC)

The inability to recognise faces is called Prosopagnosia. Graeme Bartlett 04:34, 12 September 2007 (UTC)

And the inability to remember names is Dysnomia. Although I'm not sure if this covers the inability to remember names (which I can relate to) when one can still remember most other things quite normally. Someguy1221 04:38, 12 September 2007 (UTC)

And a realted thing is tip-of-the-tongue (TOT) phenomenon, when you cannot recall on time when you need to say it, but it is in the memory hidden away. Graeme Bartlett 04:43, 12 September 2007 (UTC)


 * Tamfang's description nails it fairly well... maybe it's just that I am using mnemonic devices for other things that I'm not fully aware of. I think Dysnomia might be the word I was looking for, thanks Someguy1221!
 * From what I understand of it, Autism would be a problem in relating to others, not naming them (a subject/subject relationship, rather than a subject/subject-as-object relation). That's sort of the problem though... people often think it's rude not to lremember their name, when it's really just a memory problem :). Probably not Alzheimer's though... I've had this problem as long as I can remember :). -- SB_Johnny | PA! 08:47, 12 September 2007 (UTC)


 * Autism isn't it - people with extreme autism wouldn't be generally likely to ask questions at the Wikipedia reference desk - and those that could would be very aware of their problems and the cause.  Try Aspergers syndrome - similar kind of thing but very commonly undiagnosed (I have Aspergers and I didn't find out until I was 45 years old!).  Dysomnia would prevent you from remembering other facts - not just names - and we know you can remember lots of other stuff very well ("a steel trap"!) - so that's not it.  But let's not stray into medical diagnoses because that would be 'A Very Bad Thing'.


 * What is much more likely to be the case (and this is a problem I have) is that when you first meet someone and they tell you their name, it simply doesn't matter enough to you to make you want to remember it...especially when you are about to launch into a complicated discussion about something. There is something bigger on your mind at the time - and the name gets crowded out.  You have to make a conscious effort to listen for the name, ask for it again if you aren't sure you got it right - repeat it back to the person - and (crucially) keep it in your head long enough for it to lock into long-term memory.  At my last company, everyone had to wear security badges with their names on them - so partway through a conversation with a stranger, I could check their tag and be sure I'd gotten their name right - that helped a lot.  Where I work now we have a database of employees with names and photos - so in the worst case I can look up their picture and get a name that way. SteveBaker 14:41, 12 September 2007 (UTC)


 * Akin to mnemonics, a tried and tested way to remember names is to make a connection with something else, preferably something absurd. For example, to remember SteveBaker's name, you could envision him as a stevedore balancing a bread on his head. But it can be simpler. A neighbour of mine is named Gideon. So I think of a bible to remember his name. Later I learned he is a Jew. Which I then added to the association. Not because it makes sense, but because it makes no sense. Does that make any sense? DirkvdM 19:43, 13 September 2007 (UTC)
 * How does that not make sense? The Gideon for whom the Bibles are named was, of course, Jewish. --Trovatore 14:57, 14 September 2007 (UTC)


 * I didn't know that, but that is totally irrelevant here. The point is that the association helps you remember the name. Whether it makes any sense is irrelevant. It actually helps if it doesn't make sense. DirkvdM 18:27, 14 September 2007 (UTC)

Rear Facing Missiles
Why don't fighters (or any other aircraft for that matter) mount rear facing missiles to use on pursuing aircraft? Since modern missiles are all-aspect they could easily track a pursuing aircraft and could be used to destroy them or at least force them to break off pursuit to evade the missile. Exxolon 22:13, 11 September 2007 (UTC)
 * There's a basic two-fold answer to this:
 * Facing only matters at close range. At intermediate or longer ranges, it's trivial to turn and face another aircraft.
 * Missiles are largely ineffective at close range, as demonstrated by the F-4 Phantom (among others) in Vietnam.
 * &mdash; Lomn 23:46, 11 September 2007 (UTC)


 * This is a complete guess, but maybe because planes fly forwards through the air, it might be aerodynamically easier for the missile initially to face forwards. --70.174.143.76 01:44, 12 September 2007 (UTC)
 * Also, a plane's targetting radar usually faces forwards, so in the absence of airborne (AWACS) or ground based radar, you would need to orient the plane towards the target to get a lock. —Preceding unsigned comment added by 138.29.51.251 (talk) 02:47, 12 September 2007 (UTC)


 * The trouble is that a rocket (unlike a bullet) leaves its launcher at zero relative speed. When you launch one backward, it's at the same airspeed as you but tailfirst, and its fins tend to flip it around.  —Tamfang 07:27, 12 September 2007 (UTC)


 * Perhaps our OP is thinking of Firefox (movie) which featured rear-firing thought-controlled missiles on the (then fictional) MiG 31. The real MiG-31 is called 'Foxhound' and has nothing particularly fancy about it!
 * I used to design simulators for F16's. F18's, F117's and F22's, so I can claim some expertise here. I don't buy most of the preceeding arguments - I think Lomn has it about right.  If they wanted rear-facing rockets, they could make them. They don't exist because they simply aren't needed.  A hypothetical rear-facing rocket would come with rearward-pointing targetting equipment.  All of these missiles have their own radar or IR camera guidance systems anyway - which the host aircraft ties into before launch in order to lock on to the target - so that's absolutely no big deal.  The missile could be equipped with fins that only popped out when its airspeed was large enough...or it could have fins at the front of the missile to keep it stabilised until it's at zero airspeed which then retract when the thing has forward airspeed.  However, these missiles accellerate at an ungodly number of g's and often have vectored thrust to help steer them.  I think they could remain stable long enough without all of that complexity.
 * The fact is that (Hollywood notwithstanding) here in the 21st century you don't chase the other guy's plane around the sky in ever decreasing circles like a world-war one biplane until you get on his tail about 100 feet away then carefully line him up in your crosshairs and shoot the missile - that's just dumb! This happens in "Top Gun (movie)" and nowhere else!  The plan is to sit around 10 to 20 miles away, line him up in your radar and shoot him down from a very great distance!  Most aircraft can simultaneously lock on, launch and fire at a handful of enemy planes at once!  Some of the more modern varients have sights built into the pilots helmet that project crosshairs onto the inside of the cockpit canopy to show where the targets are as he turns his head to look at them.  Even if you are facing the wrong way - if you aren't right up close then you can shoot the missile forwards, have it go around in a nice gentle curve and whack the guy who is behind you.  The pilot pretty much chooses who to hit and the aircraft, sensors and missiles figure out how to do it.  Missiles go much faster than a plane and can turn way more sharply - why chase the enemy with an aircraft when you can keep your expensive plane and vulnerable pilot a nice long way away - and chase the bad guy with a homing missile?  This is really not a problem with modern technology.  For the most modern aircraft, air-to-air combat is pretty much an irrelevence (except maybe for taking down helicopters) - these days the big concern is ground attack - and rear-mounted missiles don't offer any kind of theoretical benefit in those cases. SteveBaker 14:23, 12 September 2007 (UTC)
 * So if I understand correctly it's really a case of this tech isn't deployed as it's not needed. Most engagements are beyond visual range and with off-boresight launching you can fire missiles behind you anyway at any appreciable range. Actual dogfighting is so rare that such as system would very rarely be of any use.
 * Of course this does beg the question of why fighter pilots have to meet such exacting requirements if all they essentially do is sit up there in the sky and program a computer to blow the enemy planes out of the sky.
 * And it's very indicative of the way modern warfare is conducted in that the individual skill of a pilot may not count for anything at all if there is a mismatch in the level of technology in use. He who has the best weapons and platform wins regardless.
 * Exxolon 19:32, 12 September 2007 (UTC)
 * There are far more applicants to be pilots than there are planes for them to fly - therefore the airforces of the world can afford to take the best applicants whether they need the best or not. To be fair, there are some tasks that require good eyesight, excellent reactions, spatial perception, etc.  Landing on a carrier deck comes immediately to mind.  Technology certainly plays a major role - not only in the plane but also in the pilot training.  Until just recently I designed the simulators that these guys learn their jobs on - one shouldn't underestimate the value of training - a fighter is a REALLY complicated machine and the pilot has an insane amount to learn in order to operate it correctly.  But the era of the manned fighter is coming to an end.  We've seen the 'spotter plane' role be taken over by the unmanned 'Predator' UAV - it can stay in the air for 36 hours and costs a tiny fraction of the cost of a manned aircraft.  Now the Predator carries air-to-ground missiles and the light ground attack role is gradually switching over to them.  It's only a matter of a few years until we start to see unmanned aircraft doing all of the dangerous 'up front' stuff in fighter and ground-attack roles.  When you take the pilot out of the plane, it gets smaller, cheaper and lighter - also stealthier and more expendable.  Many modern fighters can pull more G's than the pilot can stand without blacking out - and getting the pilot out of the machine can only help.  I think we have maybe a decade to go before we have no more fighter pilots in the USAF. SteveBaker 03:12, 13 September 2007 (UTC)
 * You could just have a device that tosses out a handful of random left-over nuts and bolts. Gzuckier 15:43, 17 September 2007 (UTC)

Water to burn
A fanous medical researcher discovered that if he exposed seawater to radio frequency energy, hydrogen was liberated and would burn. The article talks about the ocean as a fuel source. So: how much energy do you expect it takes to break the hydrogen bonds, compared to the energy derived from burning the hydrogen? Edison 23:29, 11 September 2007 (UTC)


 * That's kind of my question. If you liberate the water using a combination of radio waves and heat, and then burn that to get water again, you're no better off energy wise.  It would be analogous to splitting water completely using electricity and then burning the hydrogen and oxygen; there is no net energy gain.  I have yet to see a scientific writeup of this, and am mostly curious why it has to be salt water (and does the kind of salt matter? ie NaCl vs. KCl vs. CaCl2). Of course these will be tested since this is a relatively recent discovery.  —Preceding unsigned comment added by Bennybp (talk • contribs) 00:07, 12 September 2007 (UTC)
 * Wikipedia already has an article on the inventor, John Kanzius. Abecedare 00:49, 12 September 2007 (UTC)
 * Are you sure it has to be sea water? The primary reason AFAIK why most attempts to liberate hydrogen from water use sea water is because there is a lot, lot, lot more sea water then there is fresh water. Many places have problems with the lack of fresh water and some people even believe there may be major wars of water in the future. However obtaining sea water is not a problem and we're not likely to run out of it any time soon. BTW, although it's true you're never going to come close to breaking even let alone having a net energy gain from liberating hydrogen, the idea is that you use some sort of environmentally friendly power source e.g. solar to generate the power used for splitting the water and you then have an environmentally friendly fuel you can use for things like cars or more generally as a energy store. Whether or not this will work out or stuff like electric cars (with batteries) and biofuels is a better idea remains an open question Nil Einne 20:22, 12 September 2007 (UTC)

I've got another idea for a great energy source: compressed springs. Get a bunch of these, in a convenient size and configuration, and every time you need some mechanical energy, release one. If you need electrical energy instead, arrange things so that the releasing spring drives a generator. When your springs are all unsprung, just squeeze them back again and start over. Presto! Infinite energy! —Steve Summit (talk) 00:49, 12 September 2007 (UTC)


 * How would you squeeze them back again? Either you would have a heck lot of manual labor or more electrical energy to run the very act of compressing the spring back. Besides, you would have to have a lot of spring to generate a sustainable amount of energy.  bibliomaniac 1 5  15 years of trouble and general madness 00:54, 12 September 2007 (UTC)
 * Exactly. You've understood the problem with the guy who's claiming to get energy out of burning seawater.  --Reuben 01:08, 12 September 2007 (UTC)


 * This keeps coming up - it's bogus. You take water - you apply a certain amount of energy to break the oxygen/hydrogen bond.  Then you burn the hydrogen into oxygen - remaking the bonds and liberating some energy and some water.  The energy to break the bond is the same as you get back when you re-form it - but your machine cannot possibly be 100% efficient - so you lose.  The first law of thermodynamics applies no matter how devious you are with using salt water and radio waves or any other wierd gadgetry (typically magnets are also involved) - and it says you can't gain energy out of thin air like this.  Think about this.  Use electricity to make radio waves, use the radio waves to split the bonds of some water and liberate oxygen and hydrogen.  Then we can burn the hydrogen in a fuel cell or something to make electricity.  Let's use the electricity to split up more water - and put the water back into the tank.  What we have here is a perpetual motion machine...unless some energy is lost in this process.  We know from the laws of thermodynamics that perpetual motion machines are impossible. So it's a given that it will DEFINITELY cost you more energy to split the water into hydrogen and oxygen than you'll be able to recover when you burn the hydrogen.  Definitely, no doubt, no debate, for sure.  So why mess around with the water and the hydrogen - let's just take the energy we'd have used to split it and use it to drive whatever it was you were going to drive with the hydrogen.  The ONLY reason to do this inherently wasteful thing is if it's more convenient to store the hydrogen than it is to store the electricity.  The problem is that too many people are enamored with the idea that somehow, if they could just come up with some tiny efficiency improvement (typically involving magnets and radio waves and such) then they could win on the deal.  In their very next breath they will say it could be used to power a car - then come the accusations of 'big oil' and car manufacturers supressing the technology, threatening their lives, etc.  Typically they'll patent their bogus contraption and then claim (to gullible investors) that "it must work because the US patent office investigated it and they say it works"... SteveBaker 02:49, 12 September 2007 (UTC)


 * That's not a proper closing tag. Steve, really! DirkvdM 09:05, 14 September 2007 (UTC)


 * To be fair, according to our article, John Kanzius "admits that his machine requires more energy than it releases". —Steve Summit (talk) 03:08, 12 September 2007 (UTC)


 * He seems to have admitted at one point that it used more energy than it released at that point, but according to the blogosphere, he's now claiming to be over unity. Unfortunately, the only sources on this are Kanzius himself and Roy, filtered through rather naive local reporters and blogs, so the signal to noise ratio here is basically zero.  --Reuben 04:07, 12 September 2007 (UTC)

There's a lot of energy potential in the ocean. We use it all the time through the magical properties of water vapor. The sun picks up part of the ocean, puts in a cloud, moves to a mountain, drops it and lets it turn a generator and then put it back in the ocean. You could then use that electricity to separate hydrogen from oxygen but that's not very efficient since it takes a lot of energy to separate those bonds. It would be better to use the electricity to separate hydrogen from fuel oil. --DHeyward 03:42, 12 September 2007 (UTC)


 * The energy there comes from the sun, not the ocean. You're describing hydropower, which doesn't take energy from the ocean at all.  -Reuben 04:07, 12 September 2007 (UTC)
 * Hello??!? Sense of humor  --DHeyward 07:20, 12 September 2007 (UTC)
 * Sorry, my fault... it's (temporarily) out of commission after seeing some of the news stories on this. --Reuben 07:42, 12 September 2007 (UTC)


 * (edit conflict)
 * It's vital to distinguish between actual energy production and mere energy storage.
 * Hydroelectric energy is, as you say, driven almost directly by the sun, which is responsible for the elevation of water vapor into the atmosphere. (It has little to do, as Reuben noted, with any "energy potential in the ocean".)
 * When we burn fossil fuels, we are in effect cashing in on solar energy captured millions of years ago by plants.
 * Electricity generated by photovoltaic cells and solar-powered heat collectors is obviously directly powered by the sun.
 * Energy derived from windmills is extracted from weather systems which are ultimately powered by the sun.
 * Geothermal energy is extracted from the latent heat of the earth's core, left over from the primordial fireball (of sorts) out of which our solar system was formed. By extracting that energy we're hastening the cooling of the planet to a degree, but of course it was cooling down anyway.
 * Nuclear energy is derived from radioactive elements left over from that same primordial cauldron.
 * Any energy we manage to extract from the tides is in a roundabout way stealing angular momentum from the moon. (But, again, that was happening anyway; we're just riding on its coattails.)
 * If we ever succeed in sustained, controlled fusion, that will be essentially "free" energy, "burning" hydrogen to helium and costing us nothing other than, in a small way, hastening the iron death of the universe. (But so far our attempts at fusion have all required quite a bit more energy input than we've gotten out, and the equipment required is decidedly not free.)
 * But just about everything else -- batteries, hydrogen electrolyzed from water, chemical energy of all kinds, springs, water pumped uphill, etc. -- is just storage, is just conversion of existing energy from one form to another. The conversion and storage may be very, very useful, but it doesn't create any new energy.  (In fact, it always loses a certain amount of energy, because no storage process is 100% efficient.) —Steve Summit (talk) 04:26, 12 September 2007 (UTC)

It is unfortunate in this day and age that all the world is controlled by powerful corporations, many of whom are intent on preventing the rise of any cheap new technology that might weaken their stranglehold on global wealth. Can you imagine what Kanzius' inventions would do to the electrical and pharmaceutical companies? If he provided proof that his inventions work, or details of their manufacture, they would be stolen out from under him, and the man himself would be brutally silenced. We should applaud him for his efforts, and provide him the support he needs to make cheap and effective sources of power, as well as the cure to cancer, available to the world populace. Someguy1221 04:21, 12 September 2007 (UTC)


 * Either your tongue's in your cheek, there, or you really haven't gotten this discussion at all. TANSTAAFL. —Steve Summit (talk) 04:31, 12 September 2007 (UTC)


 * All I've seen so far are you guys reiterating the version of science that's been fed to you by the government and multinational corporations. Someguy1221 04:39, 12 September 2007 (UTC)


 * Well, actually, no.
 * I don't expect to convince you, but the key difference between science and other, faith-based systems of thought is that you do not have to take science on faith. Many people do, of course (and this is rather sad), but when I say that perpetual motion is impossible and that you can't create free energy from nothing, I am most certainly not just regurgitating something I've read (much less something I've been fed).  I understand this stuff, it makes sense to me, it all hangs together as part of a huge interwoven tapestry of scientific ideas, all supporting and reinforcing each other, all confirmed directly by empirical evidence or by ironclad logical chains firmly rooted in empirical evidence.
 * Scientific truth is not just another belief system which you're free to choose or not choose based on fashion or sociopolitical whims or what feels good or who shouts the loudest. If you understand science, really understand it (and anyone can), the chances that there's something so wrong with it that a heretical result such as perpetual motion might actually be possible are precisely 0.000000000%. —Steve Summit (talk) 04:53, 12 September 2007 (UTC)


 * Ummm SomeGuy, do you seriously mean to say you believe that conservation of energy is a myth dreamed up by the government and multinational corporations? Really now?  I hope this is just another case of my tongue-in-cheek detector being out of alignment, and that you're not serious. --Reuben 07:16, 12 September 2007 (UTC)


 * Oh, forgive me; I forgot to bracket my response with ... Someguy1221 08:36, 12 September 2007 (UTC)
 * That's good because I was just about to mentally bracket it with ! SteveBaker 13:50, 12 September 2007 (UTC)


 * Ah, that's better. :) DirkvdM 09:05, 14 September 2007 (UTC)


 * There are really two questions here:
 * 1. Is electrolysis involved?
 * 2. Is more energy generated than put in?
 * As for #1, I'm skeptical, but it's conceivable. He's reportedly using ~14 MHz (quoted here from one of the videos).  It only takes a few V across salt water to get H2 and O2, so the voltage is easily sufficient.  That's also true in a microwave oven at 2.45 GHz, yet your microwave oven doesn't generate hydrogen gas when you use it to boil water.  It would be spectacularly dangerous if it did!  60 Hz has been reported to work (although perhaps not as efficiently as DC).  The question then is whether or not 14 MHz is a low enough frequency to have any significant effectiveness in electrolysis.  It's a question of the time constants for mass transport.  It seems unlikely, but not impossible.  Alternative hypotheses: something akin to a microwave plasmoid?
 * As for #2, not on your life. If he's right, he's using RF energy to break apart H and O in water, and then burning the hydrogen to make water.  If it were able to generate net energy, as Kanzius does appear to be claiming, it would be a perpetual motion machine of the first kind.  In this house we obey the laws of thermodynamics!  --Reuben 08:06, 12 September 2007 (UTC)


 * In a very important sense - it doesn't matter a damn how his machine works. It can't be an 'over unity' device because of the first law of thermodynamics - and it can't be "extracting energy from water" because the net result of burning the hydrogen is water so any (hypothetical) energy he extracted would have to be put back in again.  So at best it's an energy conversion/storage device.  Looking at it in that regard (which is the most charitable thing I can manage), it's only really useful if there were an abundant source of these radio waves out there that was going to waste - and there isn't.  Failing that, you'd have to make the radio waves using electricity.  On a very large scale, that could be 98% efficient - but we don't know how much of the radio energy goes into splitting up the water and how much is wasted in other ways.  If you just want to take electricity and use it to split water into hydrogen and oxygen then you'd use electrolysis.  Electrolysis (done right) is about 70% efficient - and theoretically, with the right catalysts and such, it could be made 94% efficient.  So I suppose it's just possible that this guy has come up with a fractionally more efficient way to convert electricity+water into oxygen+hydrogen.  It's not breathtakingly, amazingly great - and it's only going to work on very large scales because small-scale radio transmitters are much less efficient than electrolysis - and we're assuming that all of the radio energy does indeed go into splitting water molecules and none into heating things up or other wasteful side-effects.  Look guys - we've seen these ridiculous claims dozens and dozens of times before - and every single time they are bogus.  That should come as no surprise because the first law of thermodynamics is one of the most solidly proven laws we have - it's been around a very long time and it has stood the test of time.  It's not likely to be broken - and if it is, it won't be in 'normal' realms of matter and energy...it'll be something in a black hole or at a quantum level or something wierd like that.  It won't be in some rinky-dink experiment with radio waves and seawater taking place in someones garage. SteveBaker 13:50, 12 September 2007 (UTC)


 * Steve, of course, the laws of thermodynamics are not broken, see the "not on your life" in my answer to #2 above. But the question remains, what is the flame?  It's actually quite surprising if RF can dissociate water.  The frequency appears to be far too high for electrolysis (you really want DC), and far too low for photolysis (you need UV).  If it were hot enough for thermolysis, the water should be boiling.  So if there really is a significant amount of hydrogen coming out, that is indeed unexpected, interesting, and worth understanding.  My guess is, this is not a hydrogen flame at all, perhaps an RF plasma of ions from the match.  --Reuben 18:19, 12 September 2007 (UTC)


 * I suspect that the flame is indeed hydrogen burning in oxygen (possibly with traces of sodium from the salt making for a pretty colour). RF (at reasonable power levels) can't dissociate water - but how do we know that our enterprising inventor didn't put some kind of induction coil/antenna into the tank to convert the RF into electricity again? Given the exceedingly dubious credentials of the "scientist" whom he demonstrated this to, it's possible that the whole thing is a total fabrication. (See below - the scientist turns out to be an 84 year old guy who believes in healing people with magnets...(why is it always magnets?!)).  The motive of these crackpots is often to pursuade gullible investors to give them money - many of them end up in front of a judge as a result of this dubious practice.  Nothing short of peer reviewed papers in long established journals and duplication of the experiment by some reputable institution should be considered as 'proof' that this event happened at all...and even then, remember the cold fusion fiasco. SteveBaker 02:59, 13 September 2007 (UTC)


 * Two problems: 1) the induction coil would still be going at the same frequency! Same issue as before!  2) I think we should give the local news reporter enough credit to suppose that he would have noticed that.  --Reuben 03:41, 13 September 2007 (UTC)


 * Actually, I've changed my mind - I watched this video of the actual demonstration: - no induction coil - and that yellow flame isn't hydrogen, it's a hydrocarbon probably.  I'm pretty sure there is some clever cheating going on here.  What's that red stuff in the bottom of the testtube at the beginning of the video?  What is the purpose of showing it with a paper towel first and then moving on to doing it without a paper towel?  I'm pretty sure now that he's actively cheating by putting something into the test tube that's actually burning away - maybe a smear of wax or some oil floating on the water.  I'm now on the side of seeing this as some clever fakery.  I'd want to see this done with a new test tube - fresh out of the box and salt water made with distilled water and sodium chloride - not pulled out of some canal where it could be polluted with who-knows-what.  But I certainly wouldn't credit a news reporter with noticing cheating - and I wouldn't put it beneath him to have deliberately looked the other way in order to get a good story. SteveBaker 12:14, 13 September 2007 (UTC)

In my experience, claims of 'over unity', 'perpetual motion', or other technological miracles usually stem from one of (or a combination of) the following factors.


 * Sheer fraud.
 * Delusion or error of various sorts:
 * Failure to accurately measure energy in or out of a system.
 * Failure to account for one or more sources of energy into the system. (Non-obvious power sources, energy stored prior to the start of measurement, etc.)
 * Failure to include all important physics/chemistry in the model chosen; failure to justify (or be aware of) any simplifying assumptions that may fail under unusual conditions. (See EmDrive.)
 * Failure to do the math correctly.


 * Genuinely new physics or chemistry that doesn't violate conservation of energy but requires an extension of our understanding of conservation principles.

The last case is very rare, and should only be considered after the other much more likely explanations have been ruled out. If we gave a scientist in 1875 a little lump of plutonium, he'd be faced with a 'perpetual motion' type of problem&mdash;not knowing about radioactivity, he'd be faced with a material that constantly generated heat without combustion or chemical reaction.

Much more often today, a self-described 'scientist' will announce his 'discovery' of a novel physical principle fabricated on the basis of sloppy experiments and wishful thinking. (An example from not-too-long-ago on the Ref Desk would be Ruggero Santilli, his magnecule theory, and his ridiculous paper, "A new gaseous and combustible form of water".) TenOfAllTrades(talk) 14:20, 12 September 2007 (UTC)

As Carl Sagan said, "extraordinary claims require extraordinary evidence", and fooling a local news reporter about science is not particularly extraordinary. --Sean 15:34, 12 September 2007 (UTC)


 * I periodically put in the effort to try to fix up Water fuel cell and Water fuelled car - it's pretty futile though because the nut-jobs on those pages mostly outnumber the (relatively) sane scientists. If you want to see some empassioned arguments in favor of all of this junk science, check out the talk pages of those two articles.  It's truly depressing reading. SteveBaker 17:17, 12 September 2007 (UTC)

Maybe I'm missing something, but I think there might be something to this. No, I'm not suggesting that he's successfully violated the first law of thermodynamics- I understand enough science to know that this law is about as solid as anything can be. If the radio energy required to do this is less than the power you get right then, this may be a useful technology for making engines. Yes, the water is just storing energy, and we're not coming out ahead in the grand scheme of things, but we already have the salt water. We can consider it effectively "free" for our purposes. And yes, I realize that eventually the burned-up stuff will need to be turned back into water, and yes, this takes energy, but the atmosphere will do this by itself if we just leave it alone, right? In other words, the work that needs done on the other side of the cycle will be done using (I presume) solar power, which is effectively "free" to us. The earth already has a water cycle which operates using energy we can consider "free", since we don't have to go out of our way to make it happen. Friday (talk) 17:36, 12 September 2007 (UTC)


 * It's not that it needs to be turned back into water, it's that the very act of burning the ("activated"?) water creates water. The reaction is hydrogen + oxygen = water + heat.  This heat would be less, or at the very most equal to, the energy required to loosen the bonds.  So you are taking water, loosening the bonds, burning it, and getting water back again.  If you just loosen the bonds (and let the atmosphere do the rest), you don't get any work out of it.  I personally find the discovery cool from a chemistry/physics standpoint, but not necessarily practical for engines, unless it was more efficient that an electric motor or something. --Bennybp 17:50, 12 September 2007 (UTC)


 * The energy is not there in the water to start with. Water is the low-energy state.  You're putting energy in to get H2 and O2, which have chemical potential energy, i.e. the energy you put in has been stored in their chemical state.  Then you burn the H2 to get H2O, going back to the low-energy state.  At most, the burning gets out as much energy as you put in.  It's exactly the same as pushing a ball up a hill, and then recovering energy as it rolls back down. --Reuben 18:19, 12 September 2007 (UTC)

I was reading the original article that our OP quoted. In there it says "Rustum Roy, a Penn State University chemist, has held demonstrations at his State College lab to confirm his own observations." - which certainly makes you think: "Wow! A serious scientist at an established university says that it works! But then it says "The scientists want to find out whether the energy output...would be enough to power a car or other heavy machinery."...which is an immediate red-flag.  If you had invented a totally revolutionary technology that produced energy in an utterly new way - why on earth would you start even thinking about putting it into a car before researching how and why it works and collecting your nobel prize?  It's a classic mark of a crackpot to move directly from experiment to functional technology without looking carefully at the intervening science.  So I looked up this Rustum Roy chap.  The first Google hit said: "Rustum Roy cannot be described by any professional label."...uh...huh...OK, that's not a good sign. "He has interwoven throughout his 60 year career..." (yeah - he's 84 years old) "...both world-class science and active participation in reforming theology and the practice of religion. He is at once a distinguished research scientist and a social activist, a societal reformer and a champion of whole person healing (CAM)."...hmmm. So what about this 'whole person healing' thing? Well, it turns out this is another of those "something magical happens with magnets" thing: "Ayurvedic Healing and the Science of Electromagnetic Healing" according to the website relating to the conferences he presented at. So the so-called scientist who is backing up these crazy claims is actually someone who was indeed once a respected scientist - but in his 80's has turned to religion and bizarroid healing-with-magnets stuff. This is not someone whose opinions I'd trust. SteveBaker 17:59, 12 September 2007 (UTC)