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December 24 edit

chain's weakest link edit

Does wikipedia have an article that reflects the principle that a chain is only as strong as its weakest link? Don't bother with Weakest Link which is about the game show. Thanks. μηδείς (talk) 01:03, 24 December 2013 (UTC)[reply]

Probably the best place to start is Structural integrity and failure. --Jayron32 01:37, 24 December 2013 (UTC)[reply]

I started here: Systems theory, (but didn't get far). ~E:71.20.250.51 (talk) 01:43, 24 December 2013 (UTC)[reply]

...But I did find some analogs: Theory of constraints (management paradigm) — Joint decision trap (political science) — Rate-determining step (chemistry) ~:71.20.250.51 (talk) 02:13, 24 December 2013 (UTC)[reply]

Not what you're looking for but you might also be interested in the Ringelmann effect which is somewhat relevant. Dismas|^(talk) 02:50, 24 December 2013 (UTC) [reply]

Yes, not strictly relevant, but indeed interesting. μηδείς (talk) 02:57, 24 December 2013 (UTC)[reply]

Orgasm edit

How is the time taken to attain orgasm (for human males) dependent on age and race, if at all? Also, does it, on an average, take males longer to reach climax than females? 117.194.249.225 (talk) 06:01, 24 December 2013 (UTC)[reply]

Classically the man is far too quick for the woman. I would expect men to slow down with age, and as they become used to their partner. I have no idea about race. StuRat (talk) 11:24, 24 December 2013 (UTC)[reply]

Reminds me of an SNL "news story" from decades back, where a young male celebrity had just gotten married: "[so and so] consummated his marriage last night, while his wife looked on." ←Baseball Bugs ^{What's up, Doc?} carrots→ —Preceding undated comment added 07:57, 25 December 2013 (UTC)[reply]

As the vast commercial success of certain selective vasodilator drugs as Viagra (sildenafil) and Cialis (tadalafil) for restoring and/or sustaining male sexual potency shows, men become less capable of maintaining an erection as time goes on, because circulation to the penis becomes increasingly restricted with age. Men are dependent on the distention of the penis by their circulatory system (what is known as an "erection") for extended sex - or for it to be initiated at all; women have a corresponding difficulty with vaginal dryness as they age but it's nowhere near as pronounced. Women do generally take longer to achieve orgasm than men, which is why considerate male lovers often engage their female partners in foreplay (gentle and extended stimulation of the clitoris and other female erogenous zones with the fingers or hand) which reduces the time required for female orgasm from the point at which actual coitus starts. loupgarous (talk) 13:19, 28 December 2013 (UTC)[reply]

Precise petrol filling edit

I've never been one of those who try to fill up to a precise cost (eg £40.00) but I'm aware that many do, even if they're paying with a card and therefore don't care about change.

The numbers on the pump go change pretty fast these days. I don't know if the pumps work more quickly or if it's just the high cost of petrol. Either way, it got me thinking that if the pump speed stayed the same, given reaction speeds, there must be a maximum price of petrol that would mean it's humanly possible to achieve precise petrol filling.

What's the maximum price? --Dweller (talk) 15:36, 24 December 2013 (UTC)[reply]

I do try to fill to an exact pound (perhaps a hangover from the days when I used to pay cash). I've noticed that it is getting increasingly difficult as the price rises, but that some pumps have a much slower fill rate if you just gently squeeze the lever. On some pumps, the cost seems to jump from £x.99 to £y.01 (where y = x + 1) without ever registering £y.00. The problem would arise when the smallest metered quantity costs more than a penny, but I would expect some exact round pounds to be achievable whatever the price, and others to be missed because metering is presumably discreet and digital. If metering is analogue, then it should be possible (with extreme care and a pump that has a variable fill rate) to achieve any exact amount however high the price. Dbfirs 16:14, 24 December 2013 (UTC)[reply]

All is explained in this classic sketch from Not the Nine O'Clock News (from those far-off days when we still had the decimal halfpenny and you could fill up your car for £5). AndrewWTaylor (talk) 18:46, 24 December 2013 (UTC)[reply]

Gee, every single pump I've ever seen has 2 modes: a) fill until you stop it, and you can slow it down by easing off the trigger, and b) you first enter the price amount you want, in dollars. When you use this mode, you see it pump rapidly until it gets about 20 cents or so short, then it slows down and inches up to the last cent, stopping exactly on $x.00. 121.221.80.146 (talk) 00:00, 25 December 2013 (UTC)[reply]

Our fuel dispenser article doesn't mention presetting of a fixed dollar amount at all - someone with a suitable reference might care to add it. (It's been a feature of every pump I've seen in Perth, Australia for as long as I can remember.) Mitch Ames (talk) 03:41, 25 December 2013 (UTC)[reply]

I wonder why they have that feature in the USA and Australia but not in the UK. Dbfirs 10:55, 25 December 2013 (UTC)[reply]

Curious - I've never seen such a feature in the UK either. Pay-at-the-pump facilities are not the norm here either; perhaps we just like to do things the old-fashioned way. I recall a Not the Nine O'clock News sketch, in which somebody put £20 of fuel in their car - as they walked away, the cashier in the kiosk pressed a button and the total on the pump changed to £20.01. Alansplodge (talk) 12:28, 25 December 2013 (UTC)[reply]

I noticed this feature was available on the newly installed pumps at my local Tesco filling station last week, Alansplodge! Can't vouch for the cashier's facility though! --TammyMoet (talk) 13:35, 25 December 2013 (UTC)[reply]

Yes, I've seen them at bigger Tesco stations, but nowhere else in London or the South East of England. Alansplodge (talk) 12:18, 28 December 2013 (UTC)[reply]

Youse guys ought to move to NJ, where concierge service at the pumps is the law, and programmable totals are the standard. μηδείς (talk) 03:45, 26 December 2013 (UTC)[reply]

I don't recall ever manually setting a maximum fill amount on a pump, and I've pumped my own gasoline/petrol from Vail, Colorado to London, England. I have had on occasion (when I didn't have a credit/debit card handy and the attendant at the gas station wasn't trusting me to come back from the pump after filling my car) to ask the attendant to set a maximum amount of gas (in terms of the total price for gas pumped). loupgarous (talk) 13:31, 28 December 2013 (UTC)[reply]

AFAIK having the ability to set the maximum amount (as well as a 'fill' option) is the norm in NZ as well as Malaysia. In fact, your post highlighted a question I've been meaning to mention namely what do they do in the UK when the pump is on prepay because of concern as you mentioned about people leaving without paying and it sounds like the answer is they can limit the amount, just not at the pump. (Although I don't realy get the 'come back' issue, I would have thought if the pump isn't on prepay you just start filling, perhaps signalling to the attendant to unlock the pump if it's unlocked.) This is fairly common in NZ particularly at night and in certain high risk areas. NZ has one of the highest rates of card usage rates in the world so the issue of exact change isn't generally an issue although I imagine many people either fill their car or set a certain amount.

Malaysia is far more cash based, and although most petrol stations have now been self service for 15-20 years IIRC, in the days when this wasn't the case it was awfully convient to just tell the attendant to fill an exact amount and as far as I know most set the limit rather than trying to do it manually (although eveen with the weak ringgit, fuel prices used to be so low that it perrhaps wasn't so hard to do it the other way). Even nowadays I don't think it that uncommon for an attendant to come and meet you, so simply being able to give them an exact amount is fairly useful. (Although IIRC, pay at the pump started to be widespread after the demise of full service i.e. 15-20 years ago, for those who do use cards. However from what I heard, they did have the flaw, mentioned in our article, of printing the full card number.)

BTW how did the US come in to this? From what I can tell, before μηδείς (who came after people brought up the US), no one mentioned the US as both our infamous Perth friend and Mitch Ames appear to be referring to the situation in Perth.

P.S. I presume these are the norm in China as well since from what I can tell, most of the pumps for sale on Alibaba do have the feature [1]. This of course likely means it's the same for new pumps at least, in many developing countries, or at least the poorer ones.

Nil Einne (talk) 20:02, 28 December 2013 (UTC)[reply]

Human eating carrion edit

Can humans eat carrion if it's well-cooked to kill all bacteria? Do we just have a preference for fresh meat, or is it life-threatening? I wonder where would the preference arise, if it were not life-threatening, but I also don't see how decomposed meat (without bacteria) can kill us. OsmanRF34 (talk) 16:15, 24 December 2013 (UTC)[reply]

Not really without significant risk. There are various bacterial toxins that are heat stable, cooking won't destroy them without destroying the meat as well. Here are various source. — Preceding unsigned comment added by Medeis (talk • contribs) 17:54, 24 December 2013

Yummm!

Otherwise known as "road kill", right? Unless you're a crow, I recommend against it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:18, 24 December 2013 (UTC)[reply]

(edit conflict) See: Roadkill cuisine (or not) ~E:71.20.250.51 (talk) 19:07, 24 December 2013 (UTC)[reply]

Carrion isn't necessarily spoiled. There is no more danger in eating a deer that was hit by a car an hour ago than a deer that was shot an hour ago. In fact, The Joy of Cooking has a section explaining how to prepare road kill for eating. (At least the edition I had on my shelf for many years did -- not certain it's in the current edition.) Looie496 (talk) 19:02, 24 December 2013 (UTC)[reply]

If Osman wasn't asking whether can we eat carrion that was otherwise not safe if we cook it well enough, what would be the point of his question? μηδείς (talk) 22:03, 24 December 2013 (UTC)[reply]

If carrion wasn't necessarily spoiled, it'd just be called meat. InedibleHulk (talk) 22:53, 24 December 2013 (UTC)[reply]

Well said Medeis. I was asking about carrion, which is dead and decaying flesh. Roadkills are a different story. The latter is not necessarily spoiled, contrary to the former, which always is. OsmanRF34 (talk) 00:22, 25 December 2013 (UTC)[reply]

I once saw a documentary that showed people collecting and eating roadkill (o)possae. No further details are available. I wasn't watching it that closely. --Kurt Shaped Box (talk) 22:39, 24 December 2013 (UTC)[reply]

Just as well. FYI, or in case you weren't being funny, opossum or possum comes from Algonquian, not Latin, and as far as I know the conventional plural is "(o)possums".[2] ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:55, 25 December 2013 (UTC)[reply]

Assuming opossum were a neuter noun, its nominative plural would be opossa in Latin. Of course it also looks like the first person present indicative of the verb oposse, "I can play dead", the preterit of which would be opotui, "I managed to play dead". μηδείς (talk) 18:10, 25 December 2013 (UTC)[reply]

Hence the motto of the Possum Lodge: "Quando omni flunkus moritati". ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:27, 26 December 2013 (UTC)[reply]

Are you sure you aren't thinking of the motto of Detroit, Quod si non possum, opossum? μηδείς (talk) 03:41, 26 December 2013 (UTC)[reply]

Oddly enough, I'm currently reading a book about Detroit. Just starting chapter 9. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:46, 26 December 2013 (UTC)[reply]

I expect to be at Chapter 13 soon. And remember, the word Detroit itself is from the French, combing the words debt + riot. StuRat (talk) 13:30, 26 December 2013 (UTC) [reply]

An observation: sometimes it is considered de rigeur to hang meat after it has been killed, in order for flavours to "develop". --TammyMoet (talk) 13:33, 25 December 2013 (UTC)[reply]

Yes, but that is done in a cold locker, after the entrails are removed, without the introduction of flies and the bacteria they carry; presumably a greatly different flora. μηδείς (talk) 18:13, 25 December 2013 (UTC)[reply]

Why do hillbillies prefer roadkill ? Because the tire tread pattern makes an excellent irrigation system for the gravy. StuRat (talk) 13:30, 26 December 2013 (UTC) [reply]

Carrion - decaying flesh - is likely inoculated with a variety of bacteria to whose toxins carrion-eaters such as vultures and opossums are immune from millions of years of natural selection, but to which humans are vulnerable. It doesn't strike me as a great idea. Cooking the meat through and through enough to degrade the bacterial toxins would also destroy much of the nutritive value of the meat itself. loupgarous (talk) 13:49, 28 December 2013 (UTC)[reply]

Why do we need to unify general relativity with chemistry? edit

A scientific theory is useful only inasmuch as it makes predictions. As all testable physical phenomena can be explained with either the theory of general relativity or chemistry, what is the necessity of devising a new theory that unifies them? What predictions could be made with a unified theory that could not already be made with the theories of general relativity and chemistry collectively? 150.203.188.53 (talk) 19:13, 24 December 2013 (UTC)[reply]

Chemical phenomena fall within the scope of relativity (some more obviously than others). To the extent that they make the same predictions, they are unified (and consistency is a hallmark of predictive science). -- Scray (talk) 19:26, 24 December 2013 (UTC)[reply]

Absolutely not. Relativity only explains the gravitational force, by far the least important of the four fundamental forces in chemical phenomena. 150.203.188.53 (talk) 19:33, 24 December 2013 (UTC)[reply]

What 150.203.188.53 said. You might as well ask why someone hasn't produced a scientific theory linking general relativity to optimizing milk production on dairy farms or to producing a really catchy pop song. General relativity is a theory about gravity, a force which at the scale of atoms and molecules is just too weak to be noticeable. Explaining why gravity works and applying that explanation to how atoms and molecules behave is about as relevant as using it to explain market fluctuations in the price of frozen concentrated orange juice. As noted above, chemical phenomena are, broadly speaking, explained by aspects of Einsteinian relativity, especially, for example, mass-energy equivalence and the photoelectric effect among others. Its just that General Relativity isn't really applicable in the chemical realm. --Jayron32 19:45, 24 December 2013 (UTC)[reply]

The OP's first two claims are pretty dubious, though. The first sentence is a summary of the philosophical position called instrumentalism, which is by no means universally held. Then the hypothesis of the second sentence is pretty much just obviously wrong, unless you're using extremely broad definitions of one or both of "general relativity" or "chemistry". (Which one explains radio, for example?) --Trovatore (talk) 20:59, 24 December 2013 (UTC)[reply]

Physicists are trying to unify these two theories (see Theory of everything and Quantum gravity for example). What predictions could a unified theory make that the theories separately could not make? 150.203.188.53 (talk) 22:58, 24 December 2013 (UTC)[reply]

Physicists are trying to unify quantum mechanics and general relativity, not general relativity and chemistry. As for what predictions the unified theory could make, hopefully it could tell us about conditions where current physics breaks down: namely, high-density and high-energy regimes. For example, what happened immediately after the Big Bang? What is the singularity of a black hole like? What happens when particles are accelerated to 14 TeV (the maximum energy of the LHC) that is not predicted by current physics? --Bowlhover (talk) 00:31, 25 December 2013 (UTC)[reply]

Quantum mechanics is another name for chemistry. Why can't we use the current theories to predict their behavior? After all, the current theories have never failed us in any of our predictions before. 150.203.188.53 (talk) 01:22, 25 December 2013 (UTC)[reply]

Quantum mechanics is NOT another name for chemistry anymore than farming is another name for cooking. There's overlap between the two disciplines, but they are not synonyms. To be trite is to be inaccurate. Keep that in mind. --Jayron32 04:51, 25 December 2013 (UTC)[reply]

What part of quantum mechanics is not chemistry? 150.203.188.53 (talk) 02:06, 29 December 2013 (UTC)[reply]

It isn't necessarily clear what a new theory might predict before you have the theory; they sometimes enable us to build things that never existed before. But I think research in fundamental physics is driven largely by curiosity. Many historical discoveries in fundamental physics turned people's world views upside down even though they had no impact on everyday life. That could happen again.

The distinction between "useful" and "useless" human activities is itself problematic. If you only think about feeding and sheltering people so that they can have kids and feed and shelter their kids until they have kids and ..., then life is pretty pointless. "Useless" activities make the "useful" activities worth doing.

General relativity is pretty much useless already—its few practical applications (like the GPS clock correction) are really calculated in a simple linearized theory, and they could just be found empirically if we didn't have that. But GR is a remarkably beautiful theory and told us something interesting and surprising about the nature of the world we live in. The linearized theory wouldn't have done that. -- BenRG (talk) 01:33, 25 December 2013 (UTC)[reply]

But GR and QM have always worked. Why make a new theory when the old ones have always worked perfectly fine? 150.203.188.53 (talk) 01:50, 25 December 2013 (UTC)[reply]

They haven't always worked. The scientific process is all about making theories, then improving them when they prove inadequate. As someone noted above, there are situations where what we have now is insufficient, for example, conditions immediately after the Big Bang. Unifying these theories could possibly provide insights that the two alone could not. Also, unification of theories is probably a product of human curiosity, the want to know why the theories work. If all current theories could be combined into a theory of everything, we might be able to begin to better explain "why are things the way they are". Bramble claw x 04:18, 25 December 2013 (UTC)[reply]

When have they ever not worked? How do you know they are insufficient to predict the conditions immediately after the Big Bang? 150.203.188.53 (talk) 04:41, 25 December 2013 (UTC)[reply]

The problem there is that general relativity uses the stress-energy tensor as the source of gravitational curvature. The stress-energy tensor is a non-quantum macroscopic field that is essentially a kind of average over macroscopic scales of what's going on at a quantum mechanical scale, and isn't meaningful at an event where the curvature of spacetime changes significantly at length and time scales that are so small that quantum effects are important.

Galaxy rotation curves are a more mundane example where the existing combination of general relativity and quantum field theory isn't adequate to explain observational evidence. Currently the most popular guess as to why theory isn't matching up well with observation is that there exists some kind of dark matter, which would require tweaking QFT to include a new kind of matter about which almost nothing is known, but other physicists are guessing that it's GR that will need tweaking, and are working toward a tweaked theory of gravity. Red Act (talk) 17:32, 25 December 2013 (UTC)[reply]

I don't know the exact mathematics behind it, but I have read that our current theories cannot predict what will happen in those conditions. Also, I'm fairly sure the theories have developed since they were first introduced, and the reason would be because they didn't work for some situation (otherwise, there'd be no need to modify the theory). Bramble claw x 19:23, 26 December 2013 (UTC)[reply]

(EC) What physicists are trying to unify is general relativity and quantum field theory, not general relativity and chemistry.

There are a lot of unsolved problems in physics, some of which might not be explainable using just the existing theories of general relativity and quantum field theory, but might be explainable by a unified theory that describes both of those. It isn't possible to know in advance whether that might be the case.

It also isn't knowable in advance what predictions a new unifying theory might make which wouldn’t be unexplainable by either general relativity or quantum field theory alone. The way things generally work is that the nature of a new theory suggests new experiments that hadn't been considered to be performed before, because they test for some obscure effects for which there previously was no reason to think might exist. For example, most of the tests of general relativity weren't thought of before general relativity was developed, because they test for effects for which there was previously no reason to think they might exist. Red Act (talk) 01:05, 25 December 2013 (UTC)[reply]

Quoting user: 150.203.188.53:

"A scientific theory is useful only inasmuch as it makes predictions." Stricly speaking, although making predictions is the main use of scientific theory , there are other uses.
"As all testable physical phenomena can be explained with either the theory of general relativity or chemistry". Physical phenomena are most often explained with classical physics, although other fields can also be used, depending on the aspect being studied. DanielDemaret (talk) 12:57, 25 December 2013 (UTC)[reply]

Our OP has asked a "why" question about science. This is a tough one: why do we need a unified theory! Well, if you're concerned only with practical application, there are many parts of science that you can discard; but in some sense, scientists everywhere are indoctrinated to believe in a particular style of inductive reasoning that provides a sort of satisfying "completeness" to our understanding of the universe. After we are thus indoctrinated, we see a few places where our theory doesn't provide a complete explanation. The study of how complex behavior evolves from fundamental interactions is one such area.

The best answer I can conceive is to direct our OP to a prominent physicist's explanation of why we use these physical models about microscopic systems: we seek to use induction and to produce theories that explain emergent behaviors at macroscopic scales. Quoting myself from the archive:

“

Here it is: Stowe's Introduction to Statistical Mechanics and Thermodynamics. I have a hardcover red copy that I refer to as my little red book of thermal physics (they changed the cover in the 2nd edition, apparently). Stowe's textbook is essentially the only physics books you will ever need (because everything else can be derived from these principles - at least in statistical ensemble - and what else matters, besides ensemble behavior?) Unfortunately, reading this text does require at least a little preparation and familiarity with some more elementary physics and mathematics concepts.

”

— Nimur (talk) 02:53, 25 October 2011 (UTC)

So, grab a copy of Stowe's book. Read his introduction to statistical mechanics. That will explain why we use such theories.

Our OP's next question is a "what" question. That's easy! What predictions require solutions that account for gravity and other fundamental interactions? Any predictions about a system in which the scale for gravity is similar to the scale for other fundamental interaction requires an accurate model for all such interactions. That is, most of the study of the early universe - a very compact region of space with a very high energy density. If our OP needs more specificity, we can start by modeling a simple interaction. Let's look at Compton scattering: a photon-lepton interaction. To the best of our understanding, there have always been photons, there have always been leptons. No current, reputable "big bang" inflation theory denies this. It is, in fact, our standard model. And if we have a big bang, then at very early times, photons and leptons were all crunched together, so they should be banging into each other all the time!

Try to follow where the classical physics models break; where we need to put quantum-mechanical models in; and at which energy scales those models break. You'll find that the scale of the early universe is actually quite inconvenient: we cannot neglect any fundamental interaction; and even then, our theories still predict spherically symmetrical, perfectly homogeneous results! At which exact size of the universe does the scattering model look more like a gravitational interaction than anything else? If you aren't using a relativistic gravity model then, you probably are making incorrect predictions.

At this point, it should be self-evident that our model is incomplete. At least, it is self-evident if you have spent many years indoctrinating yourself with the mindset of a physicist. When you see an empty room, you're thinking of the virial theorem. When you see a sunrise, you are watching angular momentum being conserved. When we talk about the early universe, your brain is already thinking about the appropriate scattering equation. ...And so on. This is a mindset that most humans never have; some are born with it, and they spend many years refining it with formal education.An early universe full of electric charge, energy, and angular momentum could very well evolve into a dispersed sea of leptons; the whole of its conservation laws are satisfied, and everything we know about entropy tells us that is what should happen. Despite the inclination we have to apply Occam's razor, and assume the universe will evolve along the simplest possible path, the universe has decided to evolve its initial energy, momentum, electric charge, and everything else, into a form that allows - at least locally - non-fundamental interactions, non-elementary particles, hydrogen atoms, stellar nucelosynthesis, koalas, and iPads. The standard model does not predict what we are observing, so we know there must be something more. It's not clear if a unification of gravity with the other elementary interactions solves this conundrum, but it is at least a path forward using analytical tools we have today. Nimur (talk) 18:59, 25 December 2013 (UTC)[reply]

What experiment could you perform to test a unified theory? 150.203.188.53 (talk) 22:48, 25 December 2013 (UTC)[reply]

For example, scientists at CERN use the ALICE apparatus to conduct experimental physics in this area. Extremely high energies at the Large Hadron Collider provide experimental constraints on hypothesized particle compositeness. If we look to recent history, the Gargamelle apparatus provided experimental evidence for electroweak unification; looking to the future, scientists at CERN already know that an apparatus to demonstrate strong force unification requires a few orders of magnitude higher energy than what we have today. The recent Gravity Probe B spacecraft also comes to mind; its purpose was to provide better experimental data to constrain particular elements in the equations that formulate a generalized theory of gravity. Many historical discoveries in high energy physics resulted from careful analysis of the results during nuclear weapons testing; today, this type of work is (legitimately) impeded by environmental and geopolitical concerns. To test "a unified theory," you need to specify exactly what you're planning to unify - which means diving into the messy details.

More to the point: can we explain those types of experiments in a few sentences? Only if we gloss over important details and paint a picture in broad brush-strokes! To understand the experiments, it is typically prerequisite to study university level math and physics, and then, to pursue graduate study in physics, and to specialize in high-energy particle physics, and to attend one of the highly-competitive specialty physics-schools (for example, CERN offers summer short-courses for graduate-level physicists). Surely, you don't think these physicists are slouching around for the ten or so years it takes to prepare for work at the bleeding edge of human knowledge of the elementary interactions of our universe!

So, sure - there absolutely are experiments to test unification theories. They are quite complex. I know just a little bit about these experiments, because I read extensively, and I used to hang around with a bunch of particle physicists. Not everybody can (or wants to) dedicate the time and effort to do that. It's sort of a lifestyle choice: you're asking some very hard questions: how much effort do you really want to spend to find the answers? The average "very smart person" usually needs five or six years of preparation before they can even ask a coherent question. Nimur (talk) 00:16, 26 December 2013 (UTC)[reply]

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