Wikipedia:Reference desk/Archives/Science/2012 March 25

= March 25 =

Why don't cars run on pure isooctane?
Since isooctane has an octane rating of 100, why aren't automobiles fueled with pure isooctane? Whoop whoop pull up Bitching Betty 02:05, 25 March 2012 (UTC)


 * I see whoop whoop is getting bored again, and posting questions for entertainment. I strongly suspect he knows more than I do that to produce pure octane would cost far more than the usual mix of hydrocarbons, and that pure octane would not provide sufficient lubrication for fule system components.  Go away whoop whoop.  Wickwack124.182.130.250 (talk) 03:04, 25 March 2012 (UTC)
 * I find most of Whoop Whoop's questions thought-provoking, although some of them are not so great. This one was perfectly fine, and the answers below are excellent. 70.59.24.75 (talk) 21:00, 28 March 2012 (UTC)


 * And besides, you only need high octane to prevent engine knocking, which is rare these days. StuRat (talk) 03:24, 25 March 2012 (UTC)
 * Any pure hydrocarbon is difficult (and therefore very expensive) to isolate from crude oil, and isooctane is only a small component of naturally occurring hydrocarbons. Interestingly, the octane rating has nothing to do with the amount of octane in the fuel mixture; it is only a comparison to a benchmark mixture of isooctane and heptane, and is actually quite subjective. - Running On Brains (talk) 20:11, 26 March 2012 (UTC)

why do quadrocopters have 4 rotors?
wouldn't 3 be optimal - then it could maneuver however it wanted, and you don't have to EXACTLY match opposing rotors in order not to get undue wobbly strain (the way you have to EXACTLY match the lengths of the 4 legs of a chair to avoid wobble, but not so for a tripod/3-legged fishing chair. 79.122.49.161 (talk) 04:09, 25 March 2012 (UTC)


 * If they didn't have four rotors, then they couldn't be called quadrocopters, but tricopters. A tricycle without a third wheel, is just a bicycle. Plasmic Physics (talk) 04:43, 25 March 2012 (UTC)


 * It is true that a 3-legged chair won't wobble, but that analogy doesn't apply to helicopters. There isn't an optimal number of blades for a rotorcraft.  The heavier the rotorcraft, the greater is the blade area required.  It is possible to increase the diameter of the blades to increase the blade area, but eventually the blade tip will approach the speed of sound so then an extra blade and reduced diameter are necessary.  When a three-bladed rotor design doesn't provide the necessary blade area, it is time to go to a four-bladed design; and when that isn't adequate it is time to go to a five-bladed design, and so on.  Dolphin  ( t ) 05:08, 25 March 2012 (UTC)


 * I'd imagine an even number of rotors makes it simpler from an engineering perspective to balance the torque created by the rotors. Not to say that an even number of rotors is actually required. Take NOTAR for example. Someguy1221 (talk) 07:54, 25 March 2012 (UTC)


 * Agreed. It's very much like the cylinders in an internal combustion engine.  While it's possible to balance an engine with an odd number of cylinders, it is harder, so most engines have an even number. StuRat (talk) 09:34, 25 March 2012 (UTC)


 * I disagree. The torque operating between the blades and the rotor shaft does not need to be "balanced".  (Newton's Third Law of Motion assures us that the torque exerted on the blades by the shaft will be exactly equal in magnitude, but opposite in direction, to the torque exerted on the shaft by the blades.)  It is true that the blades constitute rotating masses that need to be balanced but that is easily achieved.  (The problem with balancing the pistons in a reciprocating engine is caused by the complex reciprocating motion of each piston, whereas the motion of each helicopter blade is purely a circular motion.)  Providing each blade is the same in dimension, weight and weight distribution, and providing the angles between each blade and its neighbour are all the same, the rotor and all its blades can rotate at high speed without causing excessive out-of-balance forces.  Dolphin  ( t ) 10:29, 25 March 2012 (UTC)
 * Since the blades experience drag against the air, a resulting torque in opposite direction is applied to the helicopter. With an equal number of rotors, resulting torque is zero. Also, when moving horizontally, the difference in lift between blades going forward and blades going backward does not produce a resulting momentum. The angle at which it flies and coupled with that the forward speed it can develop can be controlled by varying the relative speed of two of the four rotors. Biggest advantage is that fixed pitch rotor blades can be used, making the construction much simpler. See Quadrotor 84.197.178.75 (talk) 13:24, 25 March 2012 (UTC)

What does intelligence really mean?
It has always puzzled me, what is intelligence? Is there any correlation between formal education and intelligent quotient? It is observed highly educated people having PhDs, including the Harvard educated, profess ridiculous views, for example, the creation "scientists" (many of them have PhDs). '''If creationists are not intelligent, how do they get PhDs? And if they are intelligent, why do they hold ridiculous views?''' Authorities sometimes espouse views which are deemed ridiculous. Why did Freud postulate ridiculous theories like penis envy or castration anxiety? Why such beliefs were developed by an intelligent psychologist and are held by people who are considered intelligent? When people who are considered more intelligent than others hold unscientific/ridiculous views, it puzzles me what is intelligence? -- Supernova Explosion   Talk  06:08, 25 March 2012 (UTC)


 * You are confusing education (and ignorance, the lack of education) with intelligence: "There's no fool like an educated fool", "An amateur makes minor errors while a professional can overcome those to move on to the grand fallacy." "BS degree first teaches you to BS, MS degree teaches More of the Same, and PhD teaches you to Pile it Higher and Deeper."


 * In theory intelligence is defined as the ability to learn, and should be unrelated to what you have actually learned so far. However, in the real world certainly people completely incapable of learning are unlikely to get a PhD, so there is some relationship between education and intelligence.  However, it's also possible to have somebody extremely intelligent with little formal education.  And, to some extent, a formal education may just teach you to believe what others think, which can crush independent thought.  Education should not increase your intelligence, but may increase your results on an IQ test, as a certain amount of knowledge, like the ability to read, is required to do well on those.  This is a fault of the testing method, though, in that it's actually measuring your knowledge, too.


 * As for degrees, beware that there are diploma mills which will grant anyone a degree who pays enough cash. Many idiots claiming to have a doctorate actually have one of those, or perhaps an honorary degree.  Also beware of people working outside their field of expertise.  A doctorate in astrophysics, impressive though it may be, does not make one any more qualified to discuss cancer cures than somebody off the street.  Also beware of old scientists.  If they got their degree 50 years ago, in many fields that makes their knowledge obsolete.


 * Then there's wisdom, which might be even more valuable than intelligence. That is, just because you know how to do something doesn't necessarily mean it's a good idea to actually do it.  (A recent Q about a nuclear-powered UAV reminded me of that.)  StuRat (talk) 08:01, 25 March 2012 (UTC)


 * Thanks for the answer! -- Supernova Explosion   Talk  08:44, 25 March 2012 (UTC)


 * David Deutsch addresses this question fairly well in his book The Beginning of Infinity. Specifically intelligence being the abillity to seek out and acquire new knowledge to address problems. Certain belief systems have self limiting aspects that prevent new production of knowledge, for example Religions, conservatism etc, by appeals to arguments from authority, divine texts, taboos/sacred cows etc. Existing knowledge is transmitted through meme replication. One can be intelligent by faithfully reproducing existing memes, but because of the belief system, new knowledge can often be seen as transgressive and is shunned due to percieving it as off limits according to their higher authorities' edicts. Sky Machine   ( ++ ) 09:01, 25 March 2012 (UTC)
 * How about this nugget: intelligence is the ability to solve and predict, related to the maximum number of variables that can be handled simultaneously? Plasmic Physics (talk) 09:36, 25 March 2012 (UTC)
 * I don't think brute force mental calculation has too much to do with it. I am thinking it is a qualitative rather than quantitative phenomenon, the brain has to distinguish between useful knowledge and non useful "noise", the better at this the brain is, the more intelligent it is. Sky Machine   ( ++ ) 19:45, 25 March 2012 (UTC)


 * Another factor in academic achievement is personal interest and motivation. When I was at university, there was a certain number of undergraduates who were there because their parents decreed that they shall get a degree. Some of them had good genes, they were very intelligent.  But they were not interested in working hard, so they did not do very well. I've known people who were not that bright overall, but were very committed and determined - and they got excellent results in exams etc.  I've known people who were intensely interested in their hobby, and ended up knowing more than professionals, for whom it was just a job. I've met a number of Ph.d's professionally, and some of them are quite one-dimensional and some quite socially inept - indicating it was interest and not intelligence that got them through their chosen field. Ratbone60.228.241.207 (talk) 12:30, 25 March 2012 (UTC)


 * You've got three or four different things confused here. Let's sort them out:
 * General intelligence, if it is a useful concept, refers in some way to how the brain works. Let's say it is something like saying a given computer is "powerful." That might make sense as a summary, but it doesn't take into account the fact that what we mean by "powerful" can actual refer to a lot of different internal metrics and how they interact with each other (e.g. processor speed, hard drive size, hard drive speed, RAM, graphics card, and so on — one realizes the limitation of claiming any one of these is the all-important factor if you drop one of the others to zero).
 * Educational attainment is the function of many things. General intelligence is surely part of it, but above a certain threshold, it is probably less important than other factors. In my experience class matters quite a lot in determining who is in a PhD program and how well they do. We should probably not overestimate the correlation between educational attainment and general intelligence. In my experience there are a few truly, innately brilliant people mulling about in the highest universities, but they are hardly the majority. Most of what makes PhD-educated people appear more intelligent than your average man on the street are very much learned habits of thinking combined with varying degrees of specialized knowledge. This is of course without taking into account the fact of diploma mills and other more or less "fake" degrees.
 * The ability of intelligent people to belief things that appear wrong to most others is fairly well-documented. Let us say that part of the reason for this is because the consensus view of reality is probably not as iron-clad as we might always like it to be, and let us say that people have tremendous capacity for believing odd things if there are personal reasons for them to do so (said reasons might be defined as "non-logical" factors — psychological, financial, political — but I would caution against assuming that the people who believe in the consensus view do so for entirely "logical" factors either).
 * You probably shouldn't be so quick to dismiss the views of Freud and other major folks of the past as obviously ridiculous. They appear obviously ridiculous only because you have a different model of the world in your head, one that has taken considerable effort to build up, and one which may itself be seen as obviously stupid in only a few decades. I think much of what Freud postulated is wrong by current understandings, but I don't think it's obviously ridiculous. If you want to find out why Freud's ideas were seen as important and convincing in his time (and still to many today), you have to do quite a bit of historical digging to conjure up the consensus view of the world of his day, and how his work fit into it and formed it. A humble person will then realize that someone will, of course, see one's own views as being "of their time" today, rather than "obviously correct".
 * Such is my take on these things, anyway, as someone who has a fancy educational degree, and someone who uses it to study "obviously ridiculous" ideas from the past... --Mr.98 (talk) 14:06, 25 March 2012 (UTC)
 * Yeah, I agree Freud's views were influenced by contemporary cultural climate, and understanding of human mind was not well-developed at that time. -- Supernova Explosion   Talk  14:38, 25 March 2012 (UTC)
 * PS, by "ridiculous" I meant arbitrary conclusion that does not arise from scientific method; not that it looks ridiculous because of my own cognitive bias. -- Supernova Explosion   Talk  14:51, 25 March 2012 (UTC)


 * Have you read Freud's actual work? He believes his theories arose from observation. He also found that in applying them, he obtained therapeutic results that confirmed them. Now, there are various ways to interpret that data, but they are not "arbitrary conclusions." There are methodological deficits, to be sure, but again, I would not conclude that Freud's methodology is a whole lot worse than many of the theories that came after him, e.g. radical behaviorism. In any case, remember that much of our current understanding of the human mind was built upon many of Freud's concepts. It's methodologically simple-minded to say, "Freud was arbitrary when it came to things we now think are wrong, but was scientific when it came to things we now think are right." The symmetrical approach would say, "if we blame Freud's cultural climate for his bad ideas, we ought to credit it for his good ideas, as well." Which starts you off on a nice long rabbit hole of thinking about where good ideas come from. --Mr.98 (talk) 15:57, 25 March 2012 (UTC)


 * There seem to be inherent problems with psychology as a science, since the type of verifiable experiments possible in the hard sciences just don't apply. The best you can do is take surveys of how effective the patients find each technique.  Even placebos don't seem to apply (would you have somebody lay down on the couch and say nothing for two hours ?), so that leaves out double-blind studies. StuRat (talk) 20:18, 25 March 2012 (UTC)


 * There's no funnier looking glass for intelligence than sports statistics. You can be the smartest nerd on the school bus, but a few seats down there's some guy who can tell you the score for any baseball game in 1934 and is probably going to grow up to be an auto mechanic.  And of course you'll never match him, because who cares?  But he'd say the same about your chemicals and your protozoa.  And while you might know how to get a good image on a confocal microscope, who are you going to be asking for help getting out of the parking lot when your car doesn't start?  Class and caste so obscure social truths, sometimes it is hard to know if they exist at all. Wnt (talk) 23:24, 25 March 2012 (UTC)


 * People are foremost social rather than rational. It's the people who had children who are your ancestors rather than the people who disagreed with everyone else. Dmcq (talk) 13:17, 27 March 2012 (UTC)

Alchohol proof/resistant?
I have drunk alchohol (not pure of course) 3 times and i didn't become drunk (and the amount i drank was enough to make others drunk) is it possible that it doesn't work on me as good as it does on others?-92.42.55.206 (talk) 20:19, 25 March 2012 (UTC)


 * Yes, although typically those who drink a lot develop more of a tolerance than those who rarely drink. The effects are also inversely proportional to body weight, and eating as you drink slows down the absorption rate.  Alcoholics also seem to have different biochemistry that makes getting drunk far harder to resist than for the average person, so a variable response to ethanol certainly exists.  StuRat (talk) 20:22, 25 March 2012 (UTC)


 * But i'm not alchoholic, i mean i've only tried it 3 times in my life, and i'm 72Kg which i think is not very heavy... i meant being naturally resistant...-92.42.55.206 (talk) 21:43, 25 March 2012 (UTC)


 * If you are a European male, 72 kg is very light, but if you are an Asian female living in Asia, 72 kg is heavy. More importantly, how drunk you are and how drunk you think you are are two different things.  It works both ways.  An inexperinced drinker can think they are sober, but reaction time testing, stress testing, etc reveals the truth.  I used to be involved in YMCA activities, including organising (supposedly) non-alcholic parties.  But we often had naughty people spike the punch.  The effect on the party was interesting.  The spikers and those in the know usually began to act drunk.  But those not in the know tended not to act drunk - they just got a bit slower.  Ratbone124.182.143.165 (talk) 22:18, 25 March 2012 (UTC)


 * "The Heineken Uncertainty Principle - It's impossible both to consume a large quantity of alcohol and to simultaneously know what that quantity is." StuRat (talk) 22:24, 25 March 2012 (UTC)


 * Hmmm, in theory this paper addresses the question - but after 10 minutes skimming it up and down I still can't see where it says anything but that alcohol gets people drunk.  Maybe with enough patience you can find an answer in there.  One thing that is funny is that they measure a definite effect of drunkenness from the placebo - on the other hand, they say nothing about the interaction of the subjects, and at least in my opinion alcohol is tremendously effective at creating a contact high, I mean, literally to the extent of being unsteady on my feet from fairly brief mingling. Wnt (talk) 23:17, 25 March 2012 (UTC)


 * Alcohol tolerance shows differences between races, so I guess you could have the set of genes that just makes it more expensive to get drunk. I've never heard of someone being completely resistant to alcohol. Joepnl (talk) 23:59, 25 March 2012 (UTC)

I was just thinking that if it has no effect that I can feel , I'll have no good reason to drink...(OP) --Irrational number (talk) 09:11, 26 March 2012 (UTC)


 * There are many good reasons for drinking, and one has just entered my head: If a fella can't drink when he's living, how the hell can he drink when he's dead? --TammyMoet (talk) 11:19, 26 March 2012 (UTC)


 * That depends. I enjoy drinking because I enjoy the wide range of alcoholic drinks out there. I don't like being drunk, especially more than slightly, so I limit my consumption. Being drunk is a hazard, rather than an objective, in my consumption of alcohol. I also find that, per unit of alcohol, spirits inebriate me less than undistilled drinks such as beer and (hard) cider. This may be due to substances other than ethanol in the 'raw' drinks. So it's worth considering what you drank, and how much of it, in determining whether you have a high or low alcohol tolerance. If you want to test this, under reasonably safe circumstances, try having 2-4 pints of ale, lager or cider at some location conveniently close to your own home, and then on a subsequent occasion, 2-3 moderately strong cocktails. Compare the results. Unless you really, really want to experiment with hangovers as well, I suggest drinking nearly as much water as beer/cider, and about three times as much water was cocktails. Also, be sure to drink in company, preferably people that you know and trust. AlexTiefling (talk) 10:48, 26 March 2012 (UTC)


 * Note that there also seems to be a difference is how alcohol tastes to different people (similar to how cruciferous vegetables taste bad to some people). To me it's extremely bitter, so I can only stand low alcohol drinks with lots of sugar, like wine coolers.  Those who can drink straight vodka must not have my genes. StuRat (talk) 20:52, 26 March 2012 (UTC)


 * I'll bet you were drunker than you thought.
 * Part of being drunk is that you lose the capacity to tell if you're drunk. Especially if you don't drink often.
 * Here's a fun test : Drink as much as you think should make you drunk, but you're convinced doesn't. Wait fifteen minutes.  Now go talk to a friend who you're sure hasn't touched a drop of alcohol.  The next day you can ask him whether or not you were drunk. APL (talk) 04:43, 27 March 2012 (UTC)

floods in ireland
On average in a year how many floods occur in ireland. out of these how many of these are flash floods and the rest big slow floods.Also what parts of Ireland get the flooding of the most of both kinds. Also which was the deadlist, costliest and most destructive floods in ireland in recorded history. --86.45.138.149 (talk) 21:57, 25 March 2012 (UTC)
 * The first question is a bit like asking how many people in Ireland are tall. The question gives the impression of meaning something, but actually doesn't. Looie496 (talk) 23:42, 25 March 2012 (UTC)


 * It is a completely fair question. Our article on floods gives some definitions, and acknowledges that there is a difference between a large puddle and a famine-causing disaster. The office of public works for Ireland gives a history of flood control and laws here: ; you may be able to find some good stats within. The rates of flash floods vs. slower floods in general have to to due with how much land is permeable, which in turn can depends heavily on urbanization and development. A scientific article describing flood frequency in Ireland can be found here: . SemanticMantis (talk) 00:18, 26 March 2012 (UTC)

Do algae need nutrients
If you grow potatoes, it helps to add fertilizers but that isn't absolutely necessary. Would you be able to grow algae commercially without adding extra NOx etc and leave it up to the algea to combine air, water and sunlight to grow? Joepnl (talk) 23:23, 25 March 2012 (UTC)


 * No life form can grow without nutrients. Carbon, hydrogen, and oxygen come from the atmosphere, but nitrogen, phosphorus, potassium, calcium, and iron need to be obtained by absorption (except for the few species that are capable of fixing nitrogen -- but I don't believe algae are among them). Looie496 (talk) 23:47, 25 March 2012 (UTC)


 * Agreed. However, those nutrients are normally found in seawater, so there's no need to add them.  Now, if you're trying to grow algae in pure distilled water, then you will need to add quite a few things.  Commercial or research algae farms probably start with seawater and then add whatever nutrients they think are deficient.  (They could also start from distilled water, but that would be a lot more expensive, since the seawater is already close to the ideal environment and distilled water is far from it.) StuRat (talk) 03:13, 26 March 2012 (UTC)


 * Quick answer: It depends. Long answer: It depends on which scale you are producing, the cultivation system you are using and the biomass densities you wish to achieve. People have been cultivating algae for a long time. Quite a lot of it happens in large open pond systems which can be simply sea water flooded basins or natural lakes (note: algae grow in both fresh and salty water). In recent years there's been quite some development in closed system cultivation (photobioreactors). These systems allow for contaminant free cultivation and the ability to achieve higher biomass levels than can be achieved with open systems. Higher biomass levels require nutrients to support and subsequently these need to be supplied seperately. If salt water is in short supply then salts need to be added to the water as well. Lastly we shouldn't forget that algae breathe CO2. This also has to be supplied seperately in closed systems. — Preceding unsigned comment added by 137.224.252.10 (talk) 07:32, 26 March 2012 (UTC)


 * What happens when you use the algae to produce oil? If you squeeze out the oil, can you reuse the remainder as fertilizer? Joepnl (talk) 18:37, 26 March 2012 (UTC)


 * You could do that. Though, algae research right now is really big on " valorization ". That is to say, to try to make money from each component of algae not just oil. Think of proteins, starches, fine chemicals, etc. Turning algae into fertilizer would be a waste of money and potential. — Preceding unsigned comment added by 137.224.252.10 (talk) 19:10, 26 March 2012 (UTC)


 * Maybe freshwater algae, but saltwater algae is likely to contain too much salt, and desalination might be prohibitively expensive. StuRat (talk) 20:54, 26 March 2012 (UTC)


 * I was thinking of a system that only needs CO2 and water to create oil, where all other elements (N, P, K, Ca, Fe) would act like a catalyst but would be continuously recycled. Provided there is enough sun, fresh water and CO2 (all pretty much for free) it would run without having to keep adding other chemicals (or even measuring the concentrations of them). But I guess 137.224.252.10 is right, and this way of "keeping it simple" would also be a waste of precious materials. Joepnl (talk) 22:34, 26 March 2012 (UTC)


 * As a side note. Don't forget that the word " algae " is a very, very, VERY broad term. It's about as discriptive as the word bacteria or plant. New species are discovered every day and we haven't yet begun to tap their potential. — Preceding unsigned comment added by 137.224.252.10 (talk) 19:13, 26 March 2012 (UTC)


 * I was referring to the simple algae with names like Neochloris oleoabundans which sounds to me like Neochloris Allthewaytothebankia :). You are right, this is a very exciting area! Joepnl (talk) 22:34, 26 March 2012 (UTC)


 * A large problem here would be recouping cost. Harvisting algae is an energy intensive process and using them as their own fertilizer would not be cost effective. For some interesting reading check out Algaculture, Dunaliella salina, Botryococcus braunii and Chlorella. — Preceding unsigned comment added by 137.224.252.10 (talk) 08:15, 27 March 2012 (UTC)


 * Thanks for all answers! Now I just need someone who could sell me live Chlorella in The Netherlands :) Joepnl (talk) 01:27, 30 March 2012 (UTC)