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August 4

Drafting

How do I denote a NPT thread (male or female) on a blueprint? (To clarify, I'm mostly proficient in drafting -- it's only this one thing that I forgot!) 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 00:53, 4 August 2016 (UTC)[reply]

Our article is Screw thread#Engineering drawing - ANSI Y14.6 is the relevant standard. See this document (page 9) for an example. Tevildo (talk) 06:13, 4 August 2016 (UTC)[reply]

Very helpful, thanks! So if I understand the document correctly, for an NPT thread I should just put the major diameter and the thread form (NPT), and all the other parameters are already implied by the thread form? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 00:04, 5 August 2016 (UTC)[reply]

Yes, as it's a standard tapered thread, no other parameters are required to specify it uniquely. Tevildo (talk) 11:48, 6 August 2016 (UTC)[reply]

Thanks! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 02:54, 7 August 2016 (UTC)[reply]

Will I be reborn if I die?

If I die, will I reborn? Could statistical fluctuations or the Poincaré recurrence theorem or something else bring me back to life (with no memories of my current life)? Will my consciousness ever cease to exist permanently? The article timeline of the far future says that in the very distant future there may be a new Big Bang that produces a universe identical to our own. 49.199.45.58 (talk) 11:32, 4 August 2016 (UTC)[reply]

Everybody hopes so; nobody knows. All religion springs from this uncertainty (sez me). {The poster formerly known as 87.81.230.195} 2.123.26.60 (talk) 13:12, 4 August 2016 (UTC)[reply]

If you lose memory of your previous lives, there's no way to test the question. However, one theory is that the "soul" of any animal seems to be a product of its biological processes. If that's so, then the soul dies with the body. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:50, 4 August 2016 (UTC)[reply]

How could the consciousness appear and disappear from a material being? Couldn't it be that's a separate matter?

And if consciousness is just something that arise, could a planet be conscious of its existence or act according to its interests too? -- Llaanngg (talk · contribs) 14:31, 4 August 2016‎ (UTC)‎[reply]

Ancient people certainly thought so. See Animism and Pantheism. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:34, 4 August 2016 (UTC)[reply]

This assumption also appears in the "Strong" form of the modern Gaia hypothesis (which form James Lovelock, the originator of the Gaia hypothesis, does not himself support). Many contemporary neo-pagans also hold to versions of it. I myself (FWIW) do not "believe" it (since as a Fortean I reject belief/disbelief as a useful intellectual approach), but do think it beneficial to behave in accordance with it.

See also Emergent property for how "things" can arise out of complex systems, and Mind-Body Dualism for the issues arising from considering the mind or soul as a separate entity "inhabiting" the brain or body. {The poster formerly known as 87.81.230.195} 2.123.26.60 (talk) 00:39, 5 August 2016 (UTC)[reply]

Even if you have no memory of your previous lives, science may still have the answer. We don't need to have experienced the heat death of the universe to know that it will happen, for example. Cosmology is perhaps unique in that sense. But according to timeline of the far future, there may be life after the heat death. 49.199.45.58 (talk) 02:15, 5 August 2016 (UTC)[reply]

Leaving aside the speculation (e.g. "what is soul"), I would like to point out a few things about the Poincaré recurrence theorem, with a classic pop science story that goes as follow.

Hungry you decides to make scrambled eggs, so you break a few eggs in a cup, and stir them so that the yolk and the white mix up. Suddenly, scientific you wonders if there is a way to recover the yolk and the white from the mixed liquid. One way to do that is to try to perfectly revert the stirring motion to put back all particles in place, but the other way is to keep stirring for a looooong time until by chance all particles fall back together.

Of course, if you do the math, the number hiding behind "loooong time" is ridiculously huge; but, since there is a finite number of particles, it is finite and so one can say (with support from the probability theory) that it will eventually happen. A similar argument states that if the universe is infinite and relatively homogeneous (i.e. we are not born in a very special place where everything else is a soup of cold, diluted hydrogen), you must have an infinity of alien clones on far away planets similar to Earth (such planets must exist if the universe has a lot of places similar to ours).

Alas, physicists have the second principle of thermodynamics which says (paraphrased) "stop dreaming". It is possible, but very unlikely, and actually so unlikely that it can be called a physical impossibility for all intents and purposes.

Said otherwise, you would readily accept that a monkey typing randomly on a typewriter could, by pure chance, produce the complete works of Shakespeare without a single typo. However, unless you have observed that incredible production process, the possibility will not cross your mind when looking at an existing and real edition of Shakespeare. Tigraan^{Click here to contact me} 15:09, 4 August 2016 (UTC)[reply]

Even worse, one of those monkeys will type exactly what Shakespeare originally wrote, and you will fail to recognize it because it doesn't match the text we've received. In fact, those monkeys will also presumably produce texts superior to those produced by Shakespeare. But we will never know. Not enough monkeys, not enough time. - Nunh-huh 21:37, 5 August 2016 (UTC)[reply]

You die and are reborn each instant of time. What you think is time may not exist in the way you think it exists. Count Iblis (talk) 19:02, 4 August 2016 (UTC)[reply]

There is no scientific theory of qualia, so there is no current scientific question to the all-important definition here: who are you? The structure of the brain changes with each new memory made, the molecules of the brain are constantly being renewed and exchanged, so are you the same person you were? And if so, then how much more alteration could be made and you are still the same person? For example, consider a split brain patient; are both hemispheres the same person they were, and as one another? The religious theory that may shed light here is atman, but where is atman and where isn't it and how can you tell? Also consider the distinctions between types of "soul" in Egyptian soul, esp. the ka or lifeforce that I've seen described as shared in a manner similar to atman vs. the ba that is the sum of one's unique actions and more akin to the Judeo-Christian notion; there is room for thinking that there are different parts of "you" with different dispositions, or which recombine as an akh in some future world; by which I might mean parallel universe. A theory of free will is also informative for defining oneself; I shouldn't rant on about my notions of its roots in eternalism with causality violations, but it is tempting. :)

Despite the nebulous and near-unprovable nature of all this, I am tempted at least to call out the absurdity of those who believe that they can "download their consciousness into a computer" while ignoring what happens to other people. A computer is nothing like a human brain; but one human brain is much like another. Does having the thing programmed somehow to parrot a few phrases and come up with similar scores on some meaningless personality or word choice test make it more you than a different human being is? I think not. Wnt (talk) 02:22, 5 August 2016 (UTC)[reply]

Science has a lot to suggest about this - but not much in the way of concrete answers. One possibility (described in Quantum suicide and immortality) is that you may never be able to die! But if there are infinities in our universe (infinite duration, infinite spatial extent, infinite numbers of big-bang/big-crunch cycles, infinite numbers of parallel universes, etc) - then it would seem to be almost impossible for there NOT to be an infinite number of "you's" that exist out there - some of which would manage to survive past your death - some of which have yet to be born. The trouble is that all of these things are currently unknowns to the very best science that we have.

The reincarnation thing is similarly tricky. If I told you that within a small fraction of a second of your death, you'd be re-born into a new body someplace else on Earth - but with no memory whatever of your former self - you'd probably say that this constituted "reincarnation" and gain considerable comfort from that. But in terms of physics, there is no difference whatever between that scenario and the situation where you die - utterly and completely - and a completely different baby is born someplace else and it utterly unconnected with you. The "connection" in the first scenario clearly doesn't involve any forces, energies, fundamental particles or anything of that nature - so as far as anything we can measure or reason logically about - the first and second scenarios are indistinguishable.

So if it helps you to believe in this kind of reincarnation - fine! Science can't prove that it doesn't happen - and couldn't prove that it does happen. It's an "unfalsifiable hypothesis" - and science has to say "We don't know - but Occam's razor says 'Probably not!'." SteveBaker (talk) 19:52, 5 August 2016 (UTC)[reply]

As with all or most religion-related questions, the problem is that the hypothesis can't be stated in a way that can be tested. The OP's first question is, "If I die, will I reborn?" The first problem is that it's when, not if. Regardless, the issue would be how to observe such. And that's where the discussion ends. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:14, 5 August 2016 (UTC)[reply]

One can address this better by providing with an (in principle) rigorous definition of "I". The only definition that makes sense is to define "I" as that aprticular algoruthm that my brain is running right at this moment. This then does mean that I'm not the same person who is typing this part of the sentence compared to the person who started typing this sentence, because the processing the brain has done in the while typing has changed the algorithm. But we can circumvent these issues by considering classes of algorithms that may arise from each other after a short time evolution in various environments. Then any theory can be put to the test as the probability that you will experience a certain experimental outcome is affected by the distribution of your copies in an infinite universe. E.g. Don Page points out in this paper how the Born rule becomes invalid in a large enough universe due to the observer having copies of himself. Count Iblis (talk) 21:41, 5 August 2016 (UTC)[reply]

Being pregnant and not knowing

Could someone (provided it's a woman) be pregnant on advanced stage (kind of over 6 months) and not know it? --Llaanngg (talk) 14:28, 4 August 2016 (UTC) [reply]

This is going nowhere.

Google "pregnant and not know it" and you'll see a number of discussions. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:32, 4 August 2016 (UTC)[reply]

The results are about 2-3 months pregnancies, and kind of forum-like. I am talking about an advanced pregnancy. Llaanngg (talk) 14:36, 4 August 2016 (UTC)[reply]

Then refine your Google search and see what comes up. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:37, 4 August 2016 (UTC)[reply]

Nothing comes up. Unless you mean those Yahoo Answers answers. It's kind of funny to go to Wikipedia, to be send to Google, to be send to Yahoo to get an answer. BTW, why are you answering, if you don't know blimp about this? Llaanngg (talk) 14:38, 4 August 2016 (UTC)[reply]

I'm giving you the advice I would take myself. Keep in mind that Wikipedia editors are heavily tilted towards the male side, and very few of us males have ever been pregnant. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:47, 4 August 2016 (UTC)[reply]

Well, up until the birth, everything is possible if you are ignorant enough (but then, an illiterate Indian teenager might not have the same access to medical information as we do). If we assume the person has reasonable knowledge of the symptoms or has the ability to look them up, they would probably consult a doctor after six months of amenorrhoea. There is a whole lot of other stuff at Maternal physiological changes in pregnancy and related articles. Tigraan^{Click here to contact me} 14:49, 4 August 2016 (UTC)[reply]

Try Googling "giving birth without knowing you are pregnant" and you will find plenty of entries, including a doctor explaining how it can happen. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:50, 4 August 2016 (UTC)[reply]

There have certainly been numerous reports of unsuspecting mothers giving birth - here is a recent one. http://www.dailymail.co.uk/femail/article-3580600/Party-girl-didn-t-know-pregnant-gives-birth-7lb-9oz-baby-boy.html Wymspen (talk) 14:53, 4 August 2016 (UTC)[reply]

"Was still having periods" - of course, that is the Daily Mail... I thought impossible to be pregnant but still have periods, and a quick search agrees with me (e.g. [1]). Tigraan^{Click here to contact me} 15:20, 4 August 2016 (UTC)[reply]

"You can't have your menstrual period while you're pregnant.Some women do have vaginal bleeding during pregnancy. Some even report intermittent bleeding that seems like a regular period to them. But vaginal bleeding during pregnancy is not the same thing as menstruation." http://www.babycenter.com/404_can-you-get-your-period-while-youre-pregnant_7102.bc Wymspen (talk) 16:44, 4 August 2016 (UTC)[reply]

Here goes Bugs again. Notice: I don't care about Yahoo Answers, or Daily Mail or similar 'sources.'Llaanngg (talk) 14:59, 4 August 2016 (UTC)[reply]

You didn't put those restrictions in your original question. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:01, 4 August 2016 (UTC)[reply]

Yep, I thought it was evident that people search for reliable sources. I apologize for being so wrong. Llaanngg (talk) 15:05, 4 August 2016 (UTC)[reply]

I thought you wanted a plausible explanation. And there are plenty of them in Google. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:06, 4 August 2016 (UTC)[reply]

See Cryptic pregnancy. It's short, but there are reliable sources there. Searching for that term specifically, and using Google Scholar, would likely turn up more. --Jayron 32 15:28, 4 August 2016 (UTC)[reply]

This is actually a question I've been meaning to ask for a while (but didn't have time because I had more important inquiries to make) -- what makes me wonder is, how can a mother-to-be not notice her baby moving inside her? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 00:11, 5 August 2016 (UTC)[reply]

Some babies just don't move very much anyway - and if you don't consider pregnancy as a possibility anything you do feel may be taken as wind or indigestion of some sort. Wymspen (talk) 10:27, 5 August 2016 (UTC)[reply]

Poverty and obesity

I recently watched a documentary about food deserts and food insecurity in America. Instead of becoming walking skeletons, the poor people become obese or overweight but very malnourished due to all the excessive, cheap, energy-dense processed food. Sometimes, they have to skip meals, because they don't have enough food in the refrigerator, and when they do have money, they cannot afford fruits and vegetables or find fruits and vegetables in the convenience stores of the city. Can poor people live off of feral cats and dogs and Canada geese? Street dogs and cats have no homes and wild geese are plentiful, so poor people can kill them for fresh meat, because they cannot afford meat. Maybe eat the crabapples and dandelions at the local public park too? Is a diet of wild dandelions, crabapples, squirrels, birds, and feral cats and dogs sufficient or deficient in adequate nutrients? 66.213.29.17 (talk) 17:18, 4 August 2016 (UTC)[reply]

It would help if you clarified your question.

Can people survive by eating <wild animal X>? Somewhat yes. Unbalanced diets will prevent you from starving, but also likely cause various problems and shorten one's life expectancy. Everyone dies at the end anyways, so I guess to "survive" it is good enough.
What would be a good "survive in the wild" diet, with "the wild" being a local park? This comes dangerously close to medical advice, which you will not receive here.

Tigraan^{Click here to contact me} 17:49, 4 August 2016 (UTC)[reply]

The motivation for this question strains credibility, but assuming that it is asked in good faith, the proper answer is that hunting of animals for food - whether those animals are conventionally hunted in the United States, like deer and wild geese, or unconventional other animals including urban wildlife - is typically regulated by the state government. For example, here in California, Canada Goose is covered by the Waterfowl Hunting Regulations. Among the interesting rules are §251.1. Harassment of Animals - "...no person shall harass, herd or drive any ... nongame bird or mammal."

Some animals, like Canada Goose, are considered "nuisance animals" and the regulations on destroying them (or hunting them for food) are significantly relaxed. This is categorically not to be interpreted as "no rules apply." Animals that are intended to be eaten are subject to inspection for safety and disease control. For example, see Mammal Hunting Regulations. Rules in your location might differ significantly.

If you're actually interested in the rules, you can contact your local municipality or state fish and game commission; or the U.S. Fish and Wildlife Service if you're interested in applicable federal regulations.

Of course, in the United States, you must comply with all rules - local, state, and Federal rules - so if you aren't sure whether your urban area has additional restrictions on hunting, you should contact your county, municipal, or other local government.

The original poster's IP address geolocates to Ohio; here's a tip from your state government: "It is illegal... to keep any animal in Ohio from the wild, except for those taken or hunted during legal hunting seasons, with proper licenses, permits, etc." Eating an animal counts as "keeping" it.

Breaking the rules to hunt food - whether in an urban area or anywhere else - is called poaching. Police can and do enforce those laws - even in urban areas - and in a lot of places, the penalties for poaching can be incredibly severe, including felony convictions and prison sentences.

Nimur (talk) 19:01, 4 August 2016 (UTC)[reply]

At a pinch the backstrap of any vertebrate is probably palatable and nutritious. Insects and many weeds are nutritious. However poor people in america are lazy and unadventurous, so they tend to eat chemically enhanced floor sweepings instead. Hth Greglocock (talk) 19:37, 4 August 2016 (UTC)[reply]

If you do something that other people don't do in the U.S., you have a good chance of going to prison for it. If you're also poor, make that a great chance. Even a middle class person can probably only pick so many dandelions at the park before they get the raised eyebrow, and not long after that, the official question as to just what they're doing. And as for stray cats... well, you'd have millions of "moralists" frothing at the mouth demanding your flesh on a platter. (They'd probably be nearly as appalled if a local shelter were selling the meat after humanely euthanizing them - animal priesthood counts for a lot, but probably not violating pseudo-kosher dietary laws) Even respectable sources put down the Chinese for eating a wide range of weird stuff, no matter how practical it may be. Wnt (talk) 02:34, 5 August 2016 (UTC)[reply]

Having lived in a culture where hunting for food was normal practice, I am aware that it is actually takes a lot of skill and experience to successfully catch wild animals and birds (though fish are a bit easier). If you are from a culture where that is not normal practice, your chance of actually managing to feed yourself by hunting is slim. Even gathering edible plants is a risky business unless you have the skill to identify what is good to eat. If desperate, do not try hunting feral cats and dogs - the pampered pets are easier to catch as they will come right up to you expecting to be stroked. Wymspen (talk) 10:34, 5 August 2016 (UTC)[reply]

Donald Trump is overweight and was recently photographed working on a bucket of KFC on his private jet. (Using a fork, yet.) Obesity is by no means confined to the poor. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:48, 5 August 2016 (UTC)[reply]

Even so I don't think he can contribute much directly to solving the problem, but A Modest Proposal might give him a pointer towards a general solution to both the malnutrition and poverty problems. ;-) Dmcq (talk) 13:57, 5 August 2016 (UTC)[reply]

He appears to have taken that advice... Tevildo (talk) 11:51, 6 August 2016 (UTC)[reply]

In an Australian context I must admit that someone on minimum wage is probably quite sensible to buy a couple of mchappy scrotum burger meal deals a day rather than spending 40 minutes foraging.Greglocock (talk) 21:17, 5 August 2016 (UTC)[reply]

"Meals here were solitary, poor, nasty, British, and short." Food deserts, my hat. Asmrulz (talk) 13:26, 8 August 2016 (UTC)[reply]

Also, "poverty" Asmrulz (talk) 13:33, 8 August 2016 (UTC)[reply]

How much does 1 and 2 km altitude affect highway mileage?

How would sea level drivers' highway mileage compare if they were allowed to drive as fast as US Westerners? (80 mph).

At equal temperatures, tire pressure (let some air out before you climb), and vehicle (let's say a generic car like a non-hybrid Corolla). And the Westerner uses whatever gas people use up there (I think it's 85 or 86 depending on the gas station's altitude unless the manual proscribes regular or they're leaving altitude soon. Not sure).

Does low air resistance help their highway mpg cause even 85mph horsepower's still far from max sea level hp? Sagittarian Milky Way (talk) 20:24, 4 August 2016 (UTC)[reply]

You might not realize it, but one factor is where you bought the car. Cars that are intended for retail sale in markets that are "high altitude" may be manufactured slightly differently. For example, older Toyota Corollas may be factory- or aftermarket- fitted with a high-altitude-compensating valve assembly. You can find information about this type of part in a mechanic's manual like the Haynes guidebooks.

Nimur (talk) 20:59, 4 August 2016 (UTC)[reply]

Minor nitpick: I think by "equal tire pressure" you actually mean "equal tire overpressure compared to the outside air".

Yes, the lower air density up there will decrease air resistance and hence decrease the power required to maintain the car at high speeds. However, less air also means that an Internal_combustion_engine car will operate outside "standard" conditions (electric cars will likely not be affected by pressure, but maybe by temperature). What I can say with 100% certainty is that you will have less power available (be it diesel or gasoline) simply because less air = less fuel burnt at stoichiometric conditions = less energy available. You can read Turbocharger and guess how it works in reverse, but an engine with a turbo usually is optimized with the turbo in mind. All in all, I am not sure the mileage would go up or down.

As Nimur said, some cars are designed to fare better at high altitudes. It can also depend on the fuel used, in particular the octane rating. Tigraan^{Click here to contact me} 08:07, 5 August 2016 (UTC)[reply]

For reference, a piston-engine aircraft like the Cessna 172S, whose fuel-injected engine is similar in many respects to a high-performance automotive engine, is expected to drop its peak output power to around 75%, or even as low as 45% at lower RPM, when operated at altitudes of 2000 meters (around 6000 feet). For reference, find yourself an official copy of the aircraft flight manual - you can buy generic copies at places like Sporty's web store or your favorite airport bookstore (or you can find some PDF from some website - just don't refer to that data for anything important!).

Unlike an automobile, a small airplane's piston engine is designed to allow for controllable RPM and fuel mixture; and engine power is measured significantly differently between propeller aircrafts and ordinary automobiles. But this indicates that you should expect a pretty significant drop in power output - and that's even on an engine that is specifically designed to operate at altitude.

Aircraft performance charts are a standard part of a pre-flight review; the effects of density altitude on performance are heavily emphasized. Before a pilot flies, she has to check what the engine performance will be at all altitudes of flight - especially for the takeoff and the landing. The aircraft engine data is very clearly published so that the effect of altitude can be computed; and of course, altitude also affects the efficiency and performance of the wings, propeller, and the humans on board the aircraft - so all that has to be accounted for as well.

Unfortunately, most automobile manufacturers do not provide such detailed engineering diagrams of how all their systems behave at all temperatures, humidities, and pressures. But based on extrapolation from a small aircraft's piston engine, it seems very reasonable to believe that an ordinary automotive engine might lose half its peak power capability when operating at high altitude. The corollary to this statement, of course, is that most automobiles are significantly over-powered, and rarely generate anywhere close to their peak power. For example, if you take a quick glance at a 2016 Toyota Corolla's power curve, you find that its advertised (e.g.) 132 hp is produced at 6000 RPM - most drivers in most conditions couldn't sustain that kind of power delivery in a Corolla for even two or three minutes! In most safe conditions, you probably wouldn't even rev up to 6000RPM for a few seconds!

If automobile engine power was measured the way airplane engine power is measured, a lot of fancy sports cars would have to be advertised with 25 horsepower engines - and the expensive sport car's engine "spec" would probably look a lot like a Corolla's spec! - but it's not really a meaningful comparison. For starters, I'd be remiss if I didn't mention cooling - automobiles can run at high RPM because they're water-cooled; air-cooled airplanes can run hot only when moving very fast. More on this topic from Episode 2558, Cooled by Air or Water, part of the Engine of Ingenuity radio series from University of Houston.

Nimur (talk) 16:10, 5 August 2016 (UTC)[reply]

FWIW, the Lycoming O-360 engine used in an aircraft isn't much like a high-performance automotive engine. It's specced with a capacity of around 6 litres, and a power output of 180 HP. Any high performance engine in a car of that capacity would have a minimum output of around 600 HP, and in a genuine high performance car (a Ferrari for example) it would probably be closer to 1000 HP. Car engines are designed to run at a frequently varying speed (revs) and rely on a gearbox to match the engine speed to the road speed. In contrast, airplane engines run at fairly consistent revs, much lower than a typical high performance car, since they use direct drive for the propellor, and so the rev range is determined by the propellor design and efficiency. When I used to drive rally cars, I frequently had my Escort Twin Cam on the rev limiter (7000 rpm) for a mile or so in the forests.--Phil Holmes (talk) 17:07, 6 August 2016 (UTC)[reply]

The C172SP uses the IO-360 (it is the fuel-injected version of the 360 series). That engine is able to generate 180 horsepower at 2500 rpm. A high-performing automotive engine like the Audi R8's V10 540hp dual-injection powerplant (which is sometimes retailed in the United States with a software upgrade to boost the same engine to 600 hp) generates about 70% of the IO-360's power - about 130hp - when operating at 2500 rpm; the Audi engine would need to run at 7800 rpm to deliver 540 hp. Meanwhile, to operate an IO-360 at 7800 RPM would be taking the Cessna out of its approved operating range; the Audi R8 can safely operate at this engine power for some period of time. On the C172S, operating at 7800 RPM would place the oil, cooling, and all the rest of the machine past the literal red line - and there's just no way to get the Lycoming engine up to those RPMs anyway. So it's not a meaningful comparison. Automotive engines are very powerful; aircraft engines are very powerful; but their respective applications call for operations at different places on the power curve. Nimur (talk) 20:54, 6 August 2016 (UTC)[reply]

Every automotive engine i have been involved with has had to demonstrate that it would run at full power on the dyno for 100 hours. So i don't get the 25hp b/s. Similarly our prototype cars are run very high speeds for hours at a time, towing a trailer with a 4 square metre frontal area. That's a durability test for the cooling system and driveline, for the engine it is a walk in the park. Incidentally virtually none of your tldr note is relevant to fuel consumption. At 80mph most modern cars would need around 60 hp, so they are operating at part throttle. So the throttle will be slightly more open than usual, reducing pumping losses. Therefore overall I'd expect a net improvement in mpg due that and aero. Greglocock (talk) 17:57, 6 August 2016 (UTC)[reply]

The relevance to fuel consumption is straightforward: aircraft engines provide the operator with direct control of the fuel mixture.

When operating aircraft engines at high altitude, the standard procedure is to reduce fuel flow rate. Lycoming publishes entire great books on this topic: for example, here's one, Fuel Mixture Leaning Procedures (1994); and I have a copy of another book published by Lycoming called The "New" Old Leaning Procedure (which you can find at fine bookstores, too; here's a preview PDF). You can save a lot of fuel - and therefore, a lot of money - if you lean out. You can also reduce carbon and soot and lead building up in your engine, improving its lifetime, preventing spark-plug fouling. But, you can also cause detonation; excessive temperatures; and if you're not careful, you can kill the engine or reduce its useful life. If the operator is stupid, he can reduce fuel mixture to zero, and the engine stops firing. An endlessly-debated question, then, is "how much fuel should you use"?

Modern automotive engine control computer units probably do something similar to lean the fuel mixture - by monitoring intake pressure or engine cylinder head temperature or exhaust temperature - but whether your vehicle actually does this depends entirely on your make and model; and whether the engineers managed to lean the automotive fuel while still complying with all other emission requirements. But I am not aware of any automotive dashboard that has a fuel mixture knob, allowing the driver to reduce fuel consumption at high altitude (or to adjust the fuel flow for any other reason). This knob, called the fuel mixture control, is a standard feature of nearly every piston-engine aircraft.

But the point is, the aircraft engine provides direct control of fuel rate. If our metric of efficiency is miles per gallon, then there absolutely exist conditions in which I can operate an aircraft engine to get better fuel efficiency than my Toyota: I can get really high where there's very little oxygen, and consequently I can keep the engine firing with very very little fuel input into the engine while still maintaining a fairly high true airspeed and ground speed. For a given distance, one can plan a flight altitude and airspeed that provides minimal travel time; one can plan for a different altitude and airspeed that yields minimal fuel-use; and one can plan for yet a different altitude that permits minimal fuel-use-per-hour. The input parameters are independently controllable. An automobile does not have this option: your only control-input is engine RPM. This is one of many instances where aviators must be really good at intuitively understanding the mathematics of control in multiple dimensions.

If my answers are "too long", then I apologize for my verbosity. If you "didn't read" them, that's your prerogative. In my defense, I did cite sources for my claims, and I'm sure I can continue to cite more sources to clarify any point.

Nimur (talk) 21:29, 6 August 2016 (UTC)[reply]

Does that mean a new car would average at least 100 continuous hours of top speed before breaking? (with KC-135-like refueling) That's at least half of the equator. Cool. How fast a car could do that? (a Bugatti can drive 269 mph till fuel exhaustion but the tires are only minutes from bursting) Sagittarian Milky Way (talk) 18:57, 6 August 2016 (UTC)[reply]

For what it is worth, an automotive engine might have been tested; but an aircraft engine is typically certified. I would posit that there is a significant categorical difference, qualitatively and quantitatively, in the technical rigor reflected by this choice of word. Nimur (talk) 21:44, 6 August 2016 (UTC)[reply]

20000km say? yes, possible, but the diff in particular would probably not survive. I don't know about tires, either. The engine would be fine. Greglocock (talk) 07:08, 7 August 2016 (UTC)[reply]