Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

May 20

Reservoirs for pumped storage hydroelectricity?

About what proportion of water reservoirs are presently configured for pumped storage hydroelectricity? How many are suitable? Enough to support 100% wind power in most countries? 71.198.176.22 (talk) 00:11, 20 May 2010 (UTC)

The article says there's 21.5 GW worth of capacity in my country -- not nearly enough to support 100% wind power. In any case, nuclear power would be much more reliable, practical and economical than wind power (though wind power could be used to supplement electricity production). 67.170.215.166 (talk) 01:03, 20 May 2010 (UTC)

I'm more interested in how many reservoirs could be converted to pumped storage during a transition to wind. I think you may be mistaken about the cost of nuclear. 71.198.176.22 (talk) 04:15, 20 May 2010 (UTC)

This article was published by Climateprogress.org, which is a self-described progressive environmentalist blog, and was also outspoken in its defense of Al Gore -- so they stand to benefit politically from supporting renewables in the face of all evidence against such policies. Clear conflict of interest, and anyone reading this article should take it with a big grain of salt. 67.170.215.166 (talk) 05:44, 21 May 2010 (UTC)

And pretty much bog-all in my country. Pretty much one, in fact. Again, not nearly enough to support "100% wind power". Tonywalton ^Talk 01:14, 20 May 2010 (UTC)

There's also Cruachan, Foyers and Ffestiniog in the UK. Loch Lomond/Loch Katrine (via Loch Arklett) could provide around 2.5hrs of average-load for the whole of the UK, for a 10m drop in water level (13km*1km at 300m elevation), however Loch Katrine is the major source of Glasgow's water supply. As for the OP's original question, as long as the tail race discharges into a large enough body of water, of the same salinity, then any conventional storage hydro station could be converted to pump storage. Another way to store electricity is to use giant sub-sea airbags, sodium sulfar batteries or to make hydrogen during windy periods. CS Miller (talk) 11:34, 20 May 2010 (UTC)

Pumped storage is more cost-efficient due to economies of scale. It could also be used for conventional hydropower when not being used for energy storage. 67.170.215.166 (talk) 05:48, 21 May 2010 (UTC)

See U.S. Electrical Grid Undergoes Massive Transition to Connect to Renewables. An excerpt:

• Baltimore Gas and Electric Co. expects to reduce peak demand by 2014 by about 1,500 megawatts, or more than 20 percent of total peak load. "That's the equivalent of a new nuclear power plant, at a fraction of the cost of building new generation," said Mark Case, senior vice president for strategy and regulatory affairs for the utility, which is preparing to deploy two million smart meters and other energy management devices across its central Maryland territory over the next four years and initiate time-based pricing.

The demand factor on most electrical grids is rather low. That is, at most times, most equipment that could be consuming electricity, is not. On traditional dumb grids, utilities cannot control when customers will decide to switch on their equipment, and most retail customers pay a flat rate for electricity regardless of the spot price of electricity at the moment. This is a recipe for market failure, as utilities are forced to purchase expensive peaking electricity during periods of high demand, and most customers have no price incentive to shift their usage away from peak hours. Smart grids let utilities convert some fraction of demand into dispatchable demand. Having the ability to reschedule some demand is equivalent to having the same capacity in grid energy storage. We can expect further progress with Moore's law to keep making equipment smarter and thus more able to follow the supply of wind and sun by seeking the lowest spot price of electricity. The belief that intermittency must severely constrain the amount of energy we can obtain from wind and sun rests largely on the assumption that power grids will never advance beyond the dumb technology of the 1970s. --Teratornis (talk) 05:48, 24 May 2010 (UTC)

Deepest manmade pool

Listening to NPR this evening brought a question to mind. They were talking about the Deep Horizon oil spill and how much pressure the human body can take under water. So, my question is what is the deepest manmade pool ever made? By "deepest" I mean from the surface of the water to the deepest point in the pool. And by "pool", I mean any manmade hole or container which was built/dug specifically to contain water. Or a quarry or other such excavation that was later filled/allowed to fill with water. Dismas|^(talk) 04:54, 20 May 2010 (UTC)

Nemo 33 holds at least one record. Viriditas (talk) 09:44, 20 May 2010 (UTC)

Another type of record: Lock (water transport)#Very large locks says "the Oskemen Lock on the Irtysh River in Kazakhstan has a drop of 42 m".[1] The reference says it is the deepest lock. PrimeHunter (talk) 13:27, 20 May 2010 (UTC)

From Open-pit mining I came across the Big Hole which has been closed since 1914 if I understand the article correctly (and I presume was allowed to fill up with water since then) but has only filled up to a level of 40metres. I don't know if the level is stable or of hundreds of years from now it could be over 200m.

Then there's Adams Mine "the deepest being 183 m (600 ft), placing it below the water table; it is currently half filled with water" so I guess that's ~90m.

Finally I found Berkeley Pit which our article says "is filled to a depth of about 900 feet (270 m) with water" so I guess that's the winner so far. I wouldn't want to swim or dive in it though since our article also says it's "heavily acidic (2.5 pH level). The pit is laden with heavy metals and dangerous chemicals, including arsenic, cadmium, zinc, and sulfuric acid". It may have been higher except "In the 1990s plans were devised for solving the groundwater problem. Water flowing into the pit has been diverted to slow the rise of the water level. Plans have been made for more extensive treatment in the future. The Berkeley Pit has since become one of the largest Superfund sites."

Edit: I also came across Mir mine which I guess is filling with water although I don't know to what depth. [2] appears to show it with water (based on our article and the details mentioned I'm pretty sure it's the same thing even if they say it's in Eastern Serbia when it's actually in Eastern Siberian).

Nil Einne (talk) 15:39, 20 May 2010 (UTC)

Do you count artificial lakes formed by dams ? Some of the tallest dams are around 300m high, so the lakes behind them are probably of similar depth. Gandalf61 (talk) 15:46, 20 May 2010 (UTC)

Super-Kamiokande's detector-pool is just over 40m deep. I'm sure either NASA (weightlessness training) or the oil-rig safety companies (dropping a helicopter body into a pool) have deeper ones. CS Miller (talk) 21:49, 20 May 2010 (UTC)

While it is not an open pit, the former coal mine at Springhill, Nova Scotia has been refilled with ground water at 18 Celsius and is now used as a massive geothermal reservoir. One shaft goes to 1325 metres depth. LeadSongDog come howl! 21:24, 21 May 2010 (UTC)

What does "Da" mean?

Link: [3] What does "Da" mean?174.3.123.220 (talk) 05:07, 20 May 2010 (UTC)

Dalton (unit). DMacks (talk) 05:28, 20 May 2010 (UTC)

In what language? use the language ref. desk not science. —Preceding unsigned comment added by 165.212.189.187 (talk) 14:36, 20 May 2010 (UTC)

In every language:) It's a scientific unit of measurement, per the cited context, not an arbitrary word. DMacks (talk) 14:43, 20 May 2010 (UTC)

Also, it means yes in Russian. --Ouro (blah blah) 19:18, 20 May 2010 (UTC)

And since (as in "since x, therefore y") in German. 67.170.215.166 (talk) 05:52, 21 May 2010 (UTC)

For readers without an easy way to see SVG diagrams, the relevant link is: File:Formation of tholins in Titan's upper atmosphere.svg. Astronaut (talk) 14:30, 21 May 2010 (UTC)

A Wikipedia search for "Da" is redirected to "DA", a disambiguation page which lists the aforementioned Dalton (unit).

-- Wavelength (talk) 14:45, 21 May 2010 (UTC)

Da also means yes in romanian.174.3.123.220 (talk) 21:56, 22 May 2010 (UTC)

And in Serbo-Croatian. 67.170.215.166 (talk) 02:46, 23 May 2010 (UTC)

While interesting, none of this relates to the original question which was correctly answered a few days ago in the first reply. Nil Einne (talk) 02:15, 26 May 2010 (UTC)

Spinning Tesla egg and stability

http://www.youtube.com/watch?v=brNBVDCeECg&feature=related Okay, so in this vid, the egg is initially spinning about one axis, but as it rotates faster it its axis of rotation (relative to the body) switches. I was wondering why this happened. I know that an object spinning about a principal axis with a minimum or maximum value for its corresponding moment of inertia will remain stable, but an egg has two moments of inertia that are equal, so I don't know what happens in this case. Thanks. 173.179.59.66 (talk) 05:40, 20 May 2010 (UTC)

Our article Tesla's Egg of Columbus cryptically refers to "gyroscopic action". The whole article is pretty poor; I don't even understand why a rotating magnetic field would cause a copper egg to rotate (does it set up induction currents in the egg that create their own field, and interact with the external one?). Buddy431 (talk) 12:44, 20 May 2010 (UTC)

You don't need to mess around with copper and magnets and all that stuff. Just take two regular hens' eggs. Hard-boil one and leave the other raw. Now spin them on their sides as fast as you can. The hard-boiled egg will gradually roll until the pointy-end is pointing straight up...the raw one will remain on it's side and stop spinning rather quickly. SteveBaker (talk) 14:44, 20 May 2010 (UTC)

That the raw egg will stop spinning is pretty clear to me. What I still don't understand is why the other egg will change orientation. I tried something with Euler's equations which I'm not sure is correct, but maybe it will be on the right track. Let the axis that runs through the end of the egg be axis 1, the axis that the egg is initially rotating in be axis 2, and axis 3 be perpendicular to the first two. These three axes will be principal axes, so Euler's equations can be applied:

${\begin{matrix}I_{1}{\dot {\omega }}_{1}+(I_{3}-I_{2})\omega _{2}\omega _{3}&=&0\\I_{2}{\dot {\omega }}_{2}+(I_{1}-I_{3})\omega _{3}\omega _{1}&=&0\\I_{3}{\dot {\omega }}_{3}+(I_{2}-I_{1})\omega _{1}\omega _{2}&=&0\end{matrix}}$

Initially, most of the spin will be in ω₂, but owing to perhaps to some pertubations or whatever, ω₁ and ω₃ are small but non-zero. Because they are small, the second term in the second Euler equation can be ignored, and we get that ω₂ is constant. Likewise, because I₃ = I₂, dω₁/dt=0 and ω₁ remains constant. However, if we differentiate the third equation and substitue the first equation into it, we arrive at the equation

$I_{3}{\ddot {\omega }}_{3}+{\frac {(I_{2}-I_{1})(I_{2}-I_{3})}{I_{1}}}{\omega _{2}}^{2}\omega _{3}=I_{3}{\ddot {\omega }}_{3}=0$

Meaning that ω₃ will increase at a constant rate. If so, then the pointy end of the egg will begin to rotate, either moving up or down depending on the sign of ω₃. However, there are still some pieces missing: first, for the egg's tip to move up, ω₃ will have to be positive, but Euler's equations seem to imply that it can just as easily be negative;, second, what causes ω₁ to increase; finally, are Euler's equations even applicable here, considering that the principal axes are themselves rotating with respect to the laboratory frame? Actually, I can see that ω₁ would increase to preserve the orientation of the egg's angular momentum, but Euler's equations seem to contradict that (and really, this is just an exercise in applying Euler's equations, so I would like to know why they don't work, or if there's a way to make them work). 173.179.59.66 (talk) 17:39, 20 May 2010 (UTC)

The difference compared to hard-boiled is a good clue--suggests that having the internal material be fluid might be key. Especially important might be that the yolk has a different density and is mobile within the object. DMacks (talk) 18:46, 20 May 2010 (UTC)

Oh, I get why the raw egg stops spinning. Centrifugal forces push the yolk to the edges of the egg, increasing the egg's moment of inertia, and so on. What remains a mystery (at least to me) is the behaviour of the hard-boiled (or copper) egg. 173.179.59.66 (talk) 18:56, 20 May 2010 (UTC)

ok stevebaker is right about the hardboiled egg (slightly excited person) another - clearly the overall axis of rotation stays the same - so angular conservation of momentum is preserved..

actually the explanation of why this happens is complex - handwaving more handwaving - it seems that instabilities in the rotation of the egg + friction lead to precession maybe not - and eventually the egg stands up (in a circularly symmetrical arragement that is stable with respect to the frictional effects that made it stand up in the first place...) - quite how the friction causes the precession effect is beyond me - perhaps someone else could give a proper explanation...? The two mathematicians were Moffat and Shimomura - perhaps someone on the maths desk has a better handle on this. (It's certainly not trivial to explain - and quite a acchievement to prove - I'm still not sure if this is finished with Critics attacked the paper because... one for the maths desk )

As for the electromagnetic - spinning - yes - it's an induction motor basically - this video http://www.youtube.com/watch?v=pgkxAQ3fPzg shows the same effect with a slightly less confusing allen key in the second half - works for most things that conduct basically.

Question - as I understand it the induction motor shouldn't work when the copper egg stands on its end since the egg is circularly symmetrical in the centre of rotation of the field - since the torque requires anisotropy in the field.. Can anyone help me with this - does the egg slow once it's upright - at most the induced electric current would rotate - but since the rotation is about the centre of symmetry of the egg when upright there will be little resistance to it changing - and little or no torque?? (ie would a copper ball spin in the same experiment??) Anyone know??77.86.115.45 (talk) 19:47, 20 May 2010 (UTC)

So does my jumble about Euler's equations have any bearing? 173.179.59.66 (talk) 01:58, 21 May 2010 (UTC)

I've asked for assistance on the maths desk about this - I'm scratching my head - I expect the explanation to be simple - but I'm not sure it is. 77.86.115.45 (talk) 02:35, 21 May 2010 (UTC)

The friction between the hard boiled egg and the table is essential for its turning upside down. Spinning an egg on ice will not show the effect. Try first to understand the behaviour of the solutions to a simpler differential equation, say the equation of motion of a damped, unbalanced wheel rotating about a fixed horizontal axis in the gravitational field,

$A{\frac {d^{2}\phi }{dt^{2}}}+B{\frac {d\phi }{dt}}+C\sin \phi =0$

where $\scriptstyle \phi \,$ is the coordinate of angular position, $\scriptstyle \scriptstyle t\,$ is the time coordinate, $\scriptstyle A\,$ is the moment of inertia of the wheel. $\scriptstyle B\,$ is the coefficient of friction, and $\scriptstyle C=mgr\,$ is the torque amplitude, $\scriptstyle m\,$ is the mass of the wheel, $\scriptstyle g\,$ is the acceleration of gravity, and $\scriptstyle r\,$ is the distance of the center of mass from the axis. The constant solution $\scriptstyle \phi =0\mod 2\pi$ is a stable equilibrium while $\scriptstyle \phi =\pi \mod 2\pi$ is an unstable equilibrium. A small perturbation of the stable equilibrium leads to damped harmonic oscillations

$A{\frac {d^{2}\phi }{dt^{2}}}+B{\frac {d\phi }{dt}}+C\phi =0$

while a perturbation of the unstable equilibrium decays at an unpredictable time:

$A{\frac {d^{2}\phi }{dt^{2}}}+B{\frac {d\phi }{dt}}-C\phi =0$

So the motion of the wheel makes a transition from spinning to oscillation before it rests in the state of minimum energy. Without friction the energy is conserved and the transition does not take place. Bo Jacoby (talk) 00:54, 23 May 2010 (UTC).

ps. See also http://www.fysikbasen.dk/English.php?page=Vis&id=79 Bo Jacoby (talk) 20:24, 23 May 2010 (UTC).

Pressure drop in branched pipe flow

I have a Y branch (both 45 degree) entering into a main duct. What is the associated pressure drop of the branch when (1)no fluid is flowing in the main duct (ie the branch is actually a sort of 'entry')? (2)fluid is flowing in the main duct? I would be grateful if anybody could give me either a correlation modelling the flow or the equivalent k factor or a relation in terms of bend loss etc Thanks —Preceding unsigned comment added by 125.17.148.2 (talk) 06:56, 20 May 2010 (UTC)

Ants

I woke up this morning to find Ants crawling all over my kitchen. I'm not sure how or why they got there as there is nothing for the blighters to eat except perhaps a few crumbs and I live two floors above ground so I'm surprised they made the effort.

Anyway, what's the best way of getting rid of them? My local hardware store has ant powder and also a spray of liquid for ants but which is better and how long will these take to work? They're only ordinary black ants, the type that are very common. GaryReggae (talk) 09:11, 20 May 2010 (UTC)

In the UK we have something called Nippon, which is a sort of gel. You put a blob of it where you saw the ants, and they are attracted to the stuff, which they consume and carry back to the nest, which then kills all the ants. It's quite funny watching all these ant drunkards queueing up to get to this stuff, and then staggering about trying to find their way home! It's about the most effective stuff I've found yet. --TammyMoet (talk) 09:25, 20 May 2010 (UTC)

Quite funny? Sounds like sadism :P Rimush (talk) 10:00, 20 May 2010 (UTC)

We occasionally get ants in our house, and use a prepackaged solid chemical composition in a plastic container. After a few hours, the ants get attracted to the trap. In a couple of days, you can see the ants are moving slower and diminishing. In a week, they should be completely gone. --Chemicalinterest (talk) 11:08, 20 May 2010 (UTC)

(edit conflict) Most sprays and powders kill ants pretty much in a few minutes - a good idea is to put in where they are getting in - like a minefield.

Other anti-ant products contain a poison that the ants carry back to the nest - thus killing the queen or whatever. These work in the longer term - and usually come in a box with a hole for the ants to get in. This is the type chemicalinterest mentions above

Googling the name of the products will probably get you the answer - the MSDS of each product should be available online - it's fairly likely that many products use the same poison - it will be mentioned in the MSDS.77.86.108.78 (talk) 11:11, 20 May 2010 (UTC)

Of course, in the long term, they'll probably keep coming back until you eliminate whatever brought them there in the first place. You know the drill: keep the kitchen clean, keep food in sealed containers (flour, sugar especially), wipe up spills immediately, etc. Buddy431 (talk) 12:39, 20 May 2010 (UTC)

I have found that putting a line of Raid around wherever they are coming in seems to work pretty well. It kills a bunch of them but presumably not the whole colony. But I don't recall getting repeat business from the same colony. --Mr.98 (talk) 14:30, 20 May 2010 (UTC)

Thanks for all your help folks! I would have bought some 'Nippon' as it is apparently very good and kills the whole colony, however my local hardware shop didn't have any so I got a spray instead which contains 'Cypermethrine'. Spray it on an ant and it kills it almost instantly. I can't figure out where they are coming in but I have sprayed the surfaces around where there seemed to be a lot of ants. I also realised what they were coming in for - I had left an empty bottle on the side with some dregs of fruit juice in - this actually proved a very effective trap - there were literally DOZENS of dead ants in there! Anyway, a couple of hours after spraying and I haven't seen any more ants. Fingers crossed! GaryReggae (talk) 18:23, 20 May 2010 (UTC)

If the ants do not carry it back to the queen, the nest doesn't die though. --Chemicalinterest (talk) 20:34, 20 May 2010 (UTC)

_{If you want to have some fun battling with them, an interesting thing to notice is that ants won't cross a line of black pepper. I have good fun in my house finding where they are getting in and lining it with black pepper and then responding to how they get around it. Not overly effective, but a good way to turn pest control into good fun.--Jabberwalkee (talk) 03:55, 21 May 2010 (UTC)}

Most of the common ant killer products are just a mix of borax, sugar, edible oil (usually peanut oil) and perhaps something fruity to get their attention. It's often sold premixed in small tins with ant-sized openings just to make extra sure that kids and pets can't get at it. Thanks for the reminder, I've got to do something about a colony in my yard. LeadSongDog come howl! 20:12, 21 May 2010 (UTC)

NaI (Tl) temperature effect

hello, it is observed that the light output from thre NaI (Tl) crystal falls with either rise or fall of temperature. can any body help why tis happen. and what is the mechanism that causing the phenmena. 59.90.213.38 (talk) 11:23, 20 May 2010 (UTC)

Thallium iodide article says that conditions to avoid are heat, so it may decompose into the elements when heated. The thallium iodide article says the NaI crystals are doped with TlI, but the NaI article says that the NaI crystals are doped with Tl (elemental?). --Chemicalinterest (talk) 11:38, 20 May 2010 (UTC)

Thallium is probably in the form of Thallium iodide - a description of the background is here [4]

Quote: Bob immediately sent off for some pure sodium iodide, and obtained a quantity of thallium iodide as well from Fort Belvoir, Virginia, where research on crystal counters was being conducted. He placed some NaI together with, as he put it, a "pinch" of thallium iodide in a crucible, and simply torched the powder. When it cooled down, he placed a small amount of the resulting glaze on a photographic plate, together with naphthalene, and repeated the irradiation experiment with the radium source. The response of the NaI(Tl), Bob told me, was tremendous. He knew then that he had found a wonderful scintillation material.

The search temp should be "Sodium iodide thallium effeciency temperature" or similar - this turns up http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B73DP-4V3M8DT-X&_user=10&_coverDate=04/15/1982&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5c38b40ce51202ea554194ce49ce42ae which states a positive efficiency gain with temperature, which is explained in terms of emmision of light being related to adjacent thallium ("thallium dimers") in the crystal. (The article is not free on the web unfortuntately). I don't know if this theory is considered broadly correct but assume it is.

For the role of Thallium dimers in the scintillation process the key article appears to be by "Van Sciver" (Name: W. J. Van Sciver) : searching "van sciver thallium dimers" helps here.

This article is typical http://ieeexplore.ieee.org/Xplore/login.jsp?reload=true&url=http://ieeexplore.ieee.org/iel5/23/4324068/04324090.pdf%3Farnumber%3D4324090&authDecision=-203

I can't find any free resources on this on the internet. This isn't my subject - hopefully someone more expert will be able to explain more.77.86.115.45 (talk) 12:08, 20 May 2010 (UTC)

Karma

Is there any way to disprove the existence of karma? TheFutureAwaits (talk) 11:59, 20 May 2010 (UTC)

I don't think so - at the simplest level : "cause and effect" most scientists would eaily accept it to be broadly true, at more human or abstract levels; such as karma obtained through thoughts or words it is probably too subjective to be scientifically analysed to the level of proof or disproof.77.86.115.45 (talk) 12:14, 20 May 2010 (UTC)

Good things happen and bad things happen. In the immediate present our actions can result in positive and negative consequences, so if I punch a bouncer at a nightclub, the chances are I'll get beaten up in return. But if the consequence is entirely unrelated to the initial good or bad deed, there is clearly no link to a magical force. It's just two random events colliding with human irrationality (just as some people believe in good luck charms). Regards, --—Cyclonenim | Chat  12:57, 20 May 2010 (UTC)

No, definitely not. Most (if not all) versions of karma allow for the effect to come in a different life than the cause (see reincarnation). To disprove karma we would have to either disprove reincarnation or show that even if reincarnation exists, it doesn't include a concept of karma. Neither of those is falsifiable. --Tango (talk) 13:56, 20 May 2010 (UTC)

I don't honestly think so. I reckon, point of fact, that it would be easier to make a convincing case for its existence, than to break the same. Immoral people do tend to attract bad outcomes for themselves, from what I have witnessed. Having a reckless disregard for other people's feelings often means you are inattentive to matters that could set you back. Vranak (talk) 14:38, 20 May 2010 (UTC)

Karma simply means that actions have consequences. You don't need to have much life experience to realize that's true. Belief in rebirth, caste, etc is not a prerequisite to appreciating the truth of karma.--Shantavira|^{feed me} 15:13, 20 May 2010 (UTC)

It's probably far too broadly defined. To disprove something you need a specific claim. You could disprove specific claims about karma. For example you could take a thousand murderers and a thousand confirmed nice people and have them play games of chance against each other and see if the nice people are more likely to win, but if that shows no proof of Karma, someone who believed karma existed would simply say that it doesn't work like that.

Beyond that, some definitions of Karma are less about mystical forces, and more about the reactions and interactions of the people around you. For those definitions of karma it's actually a real effect caused by human's social instincts.

This sort of thing is why scientists try at all times to be very specific about their definitions. Laymen often interpret it as nit-picking, or trying to wiggle out of making a firm statement, but it's really just an important first step. APL (talk) 15:19, 20 May 2010 (UTC)

I think it would be fair to make a very reserved, but testable, claim that captures the overall principle: for example, "people who do nice things for others tend to get rewarded." Now, even this claim has some issues. What counts as a "nice thing"? What counts as a reward? To what extent do we intend to show a correlation? To what extent do outliers discredit the hypothesis? (There are plenty of nice people who have come to tragic ends). But at least this makes a stride towards a falsifiable, testable hypothesis. A scientist can then proceed to test the validity of the hypothesis. Game theory has contributed a significant body of research modeling and estimating peoples' behaviors and rewards. Surely there are also sociological papers that research this effect: The modeling of sharing: Effects associated with vicarious reinforcement, symbolization, age, and generalization. Now, to what extent does this capture the concept of karma? Karma is a vaguely defined semi-philosophical/semi-religious concept with thousands of interpretations. But if you want to restrict the claim to the concept that good behavior statistically yields better outcomes (with numerous caveats and exceptions), then that is a scientific claim with a good deal of evidence to support it. Nimur (talk) 16:23, 20 May 2010 (UTC)

Certainly one could imagine a statistical test for this. However, I suspect that the results would "prove" that Karma exists - in as much as people who do nice things tend to do better in life. But separating out the psychological feeling of well-being you get from doing someone a good turn from some mystical/religious interpretation would be much harder. How would you eliminate this "placebo effect"? There is also the issue of correlation versus causation. Could it be, for example, that people who are doing well in life tend to be nicer towards others? That seems like a reasonable hypothesis. We'd also have to be much more careful about the meaning of the term than is generally accepted. For example, we might try to devise a kind of double-blind study where people perform some act which they think is a good act - but which for reasons they aren't told is actually either "good" or "utterly evil"! If you found that those people that unknowingly were behaving in an evil manner did worse in life than the ones doing actual good in the world - then you'd have a very different conclusion than if they each performed equally. But do the "rules" of Karma say that merely having good intentions is enough to win you the rewards even if your actions are doing horrible things? If so then we can't use that test. SteveBaker (talk) 21:02, 20 May 2010 (UTC)

I'd argue the opposite of what most people seem to be saying. Bad things happen to good people. Wars and natural disasters don't spare "good people". Of course then you could argue that good people get a better afterlife or reincarnation, including that makes it completely unfalsifiable. Forgetting the subjectivity of what it means to be "good" to begin with..Vespine (talk) 22:35, 20 May 2010 (UTC)

Bad things do happen to good people - the question is whether they happen disproportionately to good people versus bad people. But this question isn't about whether Karma is 'real' or not - it's about whether you can test the hypothesis scientifically. Also, the "reincarnation" thing is a red herring - according to the believers, good karma brings rewards in this life as well as future reincarnations. Read Karma for a proper description. Note in particular: "In Eastern beliefs, the karmic effects of all deeds are viewed as actively shaping past, present, and future experiences."...if that's a true belief, then the effect should be measurable in "this life" and should not require the additional testing of any reincarnation hypotheses. If one were able (for example) to provide strong statistical evidence that karma doesn't work in this life - then you would have disproved the present belief system that surrounds it.

It is of course always possible (indeed probable) that the religious nuts would then back off a bit in a typical "god-of-the-gaps" fashion and say "Well, we're really talking about 'karma-2.0' in which the benefits of the good deeds you do in this life only affect you in subsequent reincarnations". But that would be a significant restatement of their present position - and I would argue, a different kind of karma than the kind they are telling us is guaranteed right now. However, even the 'karma-2.0' definition could (in principle) be testable (although it would be extremely difficult). You could have an entire generation of all of humanity do nothing but good deeds for their entire life - and have their children do nothing but evil their entire lives. Then you could measure the statistical improvement in the lives of the subsequent generations as the do-gooders died off and were reincarnated, then the evil-doers died and reincarnated. If the 'karma-2.0' theory is correct then the graph of newborn babies doing better than expected, then worse than expected should precisely match the graph of the deaths of the do-gooder and do-evil generations. So the hypothesis is falsifiable...but not by any practical experiment. SteveBaker (talk) 12:56, 21 May 2010 (UTC)

Sorry to object, but even if you ran that experiment, the believers could simply claim that 'soul', unlike our body, is not bound temporally. That means a soul can be reincarnated at ANY time, past, present or future. I have already heard this view given as a reason why more then one person can be the reincarnation of Julius Cesar or Elvis or whatever. This view would make it impossible to track reincarnation with the passage of time and generations. (Taken to its logical conclusion this means we could all actually be one soul, but that's another kettle of fish. ) Vespine (talk) 05:11, 24 May 2010 (UTC)

Defocus calculation

I have a lens which is focused to 5 feet. There are two points of light, one 3 feet away and another 6 feet away. How would I calculate the defocus blur (like the spread) of those points of light at the film plane given a focal length and aperture? How would I generalise this to work at all focus distances, including infinity? Lewis Collard! (lol, internet) 12:15, 20 May 2010 (UTC)

Probably the easiest way to see how to do the calculation is to draw a diagram. Light spreads from the point and hits every part of the lens. All the light that hits the lens gets redirected toward the focal point, so the size of the beam just past the lens starts out at the full size of the aperture and then decreases linearly down to zero between there and the focal point. Past that it grows again at the same rate. Use the formula on the focal length article to find the proper distance of the screen from the lens to get a focused image for the light at 3 feet, and compare that to the actual distance. Rckrone (talk) 17:13, 20 May 2010 (UTC)

There might be a suitable formula in Circle of confusion depending on exactly what info. you needed.77.86.115.45 (talk) 18:45, 20 May 2010 (UTC)

An easier way to see what's going on is to trace rays backwards from the film. All rays from a point on the film are refracted in the lens and reconverge to a point in the focal plane, then diverge beyond that. This traces out a double cone with one base at infinity and the other base at the aperture (and with the aperture's size and shape). Any light source inside that cone (and only those light sources) will make a spot on that point of the film. This is easy to remember and visualize and it tells me what I usually want to know: how much blurring will happen at a given distance, in units of physical length at that distance. It also tells you the behavior at infinity: the angular confusion at infinity is the apex angle of the cone. If you want the size perspective-scaled to a different plane for some reason, then you need to multiply by d/D, where d and D are the distances from the lens to the plane of interest and the plane of the light source, respectively. If d is the film plane, and you want to calculate it from the focal plane distance L and the focal length f, then d = 1 / (1/f − 1/L). Only these more complicated formulas appear in the circle of confusion article, together with more complicated diagrams, making things look much harder than they really are. -- BenRG (talk) 21:55, 20 May 2010 (UTC)

(more complex/accurate method) If you want to know the 'shape' of the defocus blur (ie the distribution of light in the focal plane) - you can do this mathematically - you need a good understanding of vectors/trigonometry/equivalent - (I assume the light points are on the focal axis) - you need to calculate the path of light as it travels from light source, is refracted in the lens, and then the intersection of the ray with the focal plane - this equation needs to be found as a function of angle the light ray makes with the lens axis - then obtaining the distribution (blur spread equation) by integrating over angle from 0 to the angle at which the ray makes with the aperture (at a given f stop)...

For parallel lines (ie point at infinity) you may need to use a slightly different integration (though assuming the light intensity of the parallel rays is constant with distance off axis is a good approximation for all normal lens) - (unless you are good enough at maths to have made your equations so that they don't "go silly" when point source distance = infinity.

You can also use a computer to help you do this (numerical integration) - there are also commercial products that do this - ray tracing or optics design - I don't know of any free ones - but no doubt they exist if you look hard enough (ask...)

Technically you need the forms of the len(s) you are using (ie the equation of the surface of the lens) - but you can simplify by just assuming a simple single lens even if your actual set is complicated and compound.. Ask if you need more..77.86.115.45 (talk) 18:17, 20 May 2010 (UTC)

Are you after a Depth Of Field Calculator? .. Vespine (talk) 22:29, 20 May 2010 (UTC) I corrected the displayed name of your link and hope you don't mind. Cuddlyable3 (talk) 23:16, 20 May 2010 (UTC)

particle board desk.

i have a particle board desk. i noticed there is "lip" where the top meets the edge there is a small gap where the veneer is glued. there are small white granules in there that appears to be a glue. is this Urea Formaldehyde? or some other type of glue. some came out and it is sticky. —Preceding unsigned comment added by Tom12350 (talk • contribs) 13:11, 20 May 2010 (UTC)

Probably the glue (aka resin) - Particle_board#Manufacturing suggests a number of possible glues, of which urea-formaldehyde is one likely possibility, I don't know of an easy way to distinguish the different glues.77.86.115.45 (talk) 14:41, 20 May 2010 (UTC)

Oh - if it's the glue holding on the veneer it may not be the same as the glue used to make the board - for wood veneers standard "wood glue" is applicable, for non-wood veneers (ie waterproof type plastic veneers) I don't know what sort of glue they use commercially.77.86.115.45 (talk) 17:59, 20 May 2010 (UTC)

For plastic veneers, it's usually some kind of contact-adhesive, I believe. Certainly when you do the job yourself, that's what the DIY stores recommend. SteveBaker (talk) 20:30, 20 May 2010 (UTC)

Yes - I've used araldite to mend these - I think (certain in some cases) the plastic veneers are produced with one side already coated with adhesive (and a peel off protective film) (ie like sellotape but much stronger) - this wouldn't be likely to produce any "white granules" - I think they will be from the particle board itself.77.86.115.45 (talk) 21:06, 20 May 2010 (UTC)

In some cases the edges are applied with hot-melt adhesives, which are usually white. If you can heat one of the droplets it may turn soft and sticky. Contact adhesives will rarely behave that way. LeadSongDog come howl! 05:22, 22 May 2010 (UTC)

i though hot-melt adhesives were clear —Preceding unsigned comment added by Tom12350 (talk • contribs) 05:45, 22 May 2010 (UTC)

What's the deal with ants and icing sugar?

Inspired by the ant question above. Is it true that ants will refuse/be unable to cross a line of icing sugar poured on the ground/floor upon which they are marching? Never had enough ants in my house to bother trying it, never felt the urge to dick around with the ants outside - but it's a factoid (folk wisdom?) that I've heard various people repeating over and over again down the years. --Kurt Shaped Box (talk) 16:04, 20 May 2010 (UTC)

Mmmh according to [5] it's a line of chalk not sugar - though I would guess they wouldn't cross a sugar line since oncee they found it their journey would be complete ("mission complete.found sugar.return to base.bring friends")...

Another possibility is ants dislike for fine powders .. eg Diatomaceous earth (also Boric acid Borax) - all of which look like sugar - could this be a source of the story??77.86.115.45 (talk) 16:17, 20 May 2010 (UTC)

I don't think that ants will refuse to eat icing sugar. Boric acid and borax are toxic to ants. --Chemicalinterest (talk) 17:33, 20 May 2010 (UTC)

Not quite the same subject but something I am curious about relating to ants - would double-sided tape be an effective way of catching them? Would they walk across it? If they refused to cross it then I imagine putting a line of it across where they enter would stop them from coming in.GaryReggae (talk) 18:25, 20 May 2010 (UTC)

Possibly.. depending on the glue used you might even find that they like the taste of it and are eating it..77.86.115.45 (talk) 18:32, 20 May 2010 (UTC)

Ants live their lives on a different scale to us. I wouldn't like to say for sure whether something that's sticky to us will also be sticky to their tiny feet... --Kurt Shaped Box (talk) 23:49, 20 May 2010 (UTC)

But isn't that the point of Flypaper? Kingsfold (talk) 11:48, 24 May 2010 (UTC)

Thanks very much for the answers so far, folks. Seems to make sense... --Kurt Shaped Box (talk) 23:47, 20 May 2010 (UTC)

Blood work accuracy

How can you tell if a lab provides accurate blood test results or just randomly spits out numbers ? Are they rated for accuracy in any way ? I'm in Michigan. StuRat (talk) 17:47, 20 May 2010 (UTC)

There some letters after the name, and stuff listed here Medical_Laboratory_Scientist#Certification_and_licensing - one way to tell if the lab is legit.. 77.86.115.45 (talk) 17:50, 20 May 2010 (UTC)

That's about whether individual technicians are qualified to do the tests, I'm more asking if the labs actually bother. If nobody outside the lab double-checks them or if there's no consequences for just faking the tests, I'd be worried about the results. My brother does delivers for such a lab, and they don't bother keeping frozen samples frozen, so that makes me wonder about the labs in general. StuRat (talk) 18:25, 20 May 2010 (UTC)

Um we're referring to the US here, the land of the massive lawsuit. Do you really think there's no consequence for just faking the test? Also if your lab uses certified or licensed medical laboratory scientists then they would surely have some obligation to ensure they don't just 'fake the test' and if they do, are likely to suffer similar penalties that other professionals failing in their professional obligations would. If you want to know if you lab has any such people on staff, you'd best ask them. Forgot to mention that I'm guessing many may also have a pathologist or two or more on staff or perhaps even in charge who is a doctor so of course has the same professional obligations as other doctors.

Edit: I'm presuming of course you've already read the obvious article Medical laboratory which mentions such things as "Accreditation is done by the Joint Commission, AABB, and other state and federal agencies. CLIA 88 or the Clinical Laboratory Improvement Amendments also dictate testing and personnel" and "Now many labs have a compliance officer with mandatory annual meetings about compliance for all employees" (although that appears to be more about defrauding the US governments and insurers and stuff), but still want more info?

Nil Einne (talk) 18:49, 20 May 2010 (UTC)

Well I don't know about the US but here in the UK as a lab scientist I'm not going to just be churning out random numbers, we churn out the results we get from our experiments. If there are discrepancies in the results, they would be done again. Most labs have individual benchmarks for each test for what is normal, i.e. how much of everything should be in the blood of someone in the condition that's presented to them. I suppose it could be different in the UK because the NHS will have shared generic lab values, but I don't see why it'd be that different in the US. Regards, --—Cyclonenim | Chat  19:13, 20 May 2010 (UTC)

Hmmm, knowing "how much of everything should be in the blood of someone in the condition" could easily lead to faking the results, a true blind test would be better, in my opinion. StuRat (talk) 14:36, 21 May 2010 (UTC)

The doctors sending samples to that lab would very quickly realise if the results they were getting didn't match the symptoms their patients were presenting with. --Tango (talk) 20:31, 20 May 2010 (UTC)

Yes, but I don't trust doctors or accreditation boards, a few bucks under the table will probably shut up any investigations. And this is the US, so I have to assume full regulatory capture of any agency tasked with regulating the labs, meaning they now work to cover up any problems found at the labs, rather than to protect the public. As for lawsuits, it seems to me that it would be impossible to question a lab's results, especially if they destroy the sample, once testing is completed. And they could always claim the doctor gave them the wrong sample. So, how can I personally verify whether a given lab gives accurate results ? Are there websites like, say, "RateMyLab.com", where people can report problems ? StuRat (talk) 21:13, 20 May 2010 (UTC)

If you don't trust doctors, why are you worried about lab tests? Surely you don't use the healthcare system, so don't have any tests run. --Tango (talk) 22:06, 20 May 2010 (UTC)

I'd like to have some simple tests done (cholesterol and such), and would rather bypass a doctor entirely, if possible, if I could find a lab that I can actually trust. StuRat (talk) 22:29, 20 May 2010 (UTC)

The thing is that doctors do not get into medical school to cause harm. If a lab scientist sent dodgy results, the doctor would know. If it's the doctor who is changing the lab results, why would they in the first place? Sure it might help some statistics ("oh look everyone in Michigan doesn't have high neutrophil counts" or something) but it would also mean putting your health at risk, and if something were to happen, others would then look at your results and find the discrepancy.

I just see no real, valid reason why labs would need to be tested for authenticity or accuracy. Regards, --—Cyclonenim | Chat  01:31, 21 May 2010 (UTC)

If you had two tests done and the results were the same then you could fairly assume that both labs were ok. If they differed then one (or both) were wrong.. Can't you get home tests for chloresterol etc nowadays anyway?? (I assume you have some faith left in the chemists that produce these? or are they under suspicion too ? :) ! )77.86.115.45 (talk) 23:13, 20 May 2010 (UTC)

I would have slightly more faith in a test which can be done completely at home (versus one you must mail back). The reason is that they could be easily double-checked for accuracy by the consumer. StuRat (talk) 23:26, 20 May 2010 (UTC)

I'm just not seeing the reason to have any mistrust in the labs themselves -- they have absolutely no motive to alter such tests, and they have the best equipment at hand to make sure the results are as accurate as possible. It should be noted that home tests can still provide false negatives and positives, and in any case, no complicated blood work can be conducted at home. The most you can do is check your glucose levels. Regards, --—Cyclonenim | Chat  02:09, 21 May 2010 (UTC)

We seem to have a fundamental difference, you inherently trust everyone until (you become aware that) they have violated that trust, whereas I don't trust anyone or anything until they prove they are trustworthy. I sure hope you don't give your bank account numbers to "rich Nigerian princes" who e-mail you that they want to deposit money in your account. :-) StuRat (talk) 14:41, 21 May 2010 (UTC)

Also, is there any evidence of the accreditation boards actually suspending or revoking lab accreditation for any cause other than lack of payment of dues ? That would help to restore my faith (somewhat). Otherwise, I have about as much faith in them as in financial rating services which provided top notch ratings to failing banks. StuRat (talk) 21:17, 20 May 2010 (UTC)

It seems to me you have a rather large distrust of the entire US health care system. If you don't trust the people who are actively out there each day to save lives and help people, who do you trust? Surely not a bureaucracy or regulatory agency... Regards, --—Cyclonenim | Chat  22:09, 20 May 2010 (UTC)

You must have missed it when I said it before, so I will repeat it.

1) I would tend to trust consumer ratings over "official" ratings, any day. So, is there a web site where labs are rated by consumers ?

2) I also said that, while I inherently mistrust them, I could be convinced that the "official" agencies are actually doing their jobs if there was some evidence that they do, such as suspensions and revocations of accreditation (for causes other than nonpayment of dues). So, is there any such evidence ? StuRat (talk) 22:26, 20 May 2010 (UTC)

In Australia, the vast majority of pathology is done by a small handful of large chain labs, or it might now even be just one: Healthscope, since they purchased Gribbles Pathology a few years ago, which was "the other" big lab. These places would have strict operating procedures and audits and stuff. I really just can't believe a lab would get away with faking tests "wholesale" for very long. What would be their motivation? To save money by just printing off tests instead of really doing them? And doctors and the regulatory organizations would "cover up" their fraud? What would be their motivation for that? The lab is paying them all off? That's just ridiculous. Sure there would be cases of negligence, or even fraud, but to suggest it's "institutionalized", with the participation and support of the WHOLE health community is what I'd call paranoia. Where I WOULD distrust blood tests is if they are provided by a naturopath or some other "alternative health" practice not in a well known accredited lab, in that case I think you have good reason to be sceptical about any blood work you get done. Vespine (talk) 22:55, 20 May 2010 (UTC)

I think you're taking me a bit too literally. I doubt that any labs fake all their results, but perhaps some fake a few, and others just do sloppy work (like the one where my brother works that never bothers to keep samples frozen, even thought they must be for accurate results). But I'm just interested to know if any action is ever taken against bad labs. That is, do they have any incentive to do a good job, or is keeping their costs down their only goal ? StuRat (talk) 23:16, 20 May 2010 (UTC)

A problem I foresee with a "consumer rating" of pathology labs is that consumers on the whole would not at all be qualified to judge the validity of lab results. You would get all the conspiracy nutters who believe in chem trails and the whole big pharma genocide rubbish giving their 2 cents when their doctor give results that doesn't confirm their paranoia. That's kinda why we trust specialists in the 1st place, like doctors, which is kind of a vicious circle. If there are no doctors you trust, maybe you should have considered a career in medicine yourself, or at least find some doctors you might get to know and trust. That's why I look at blogs like science based medicine, because there are doctors there who's opinions I trust. Vespine (talk) 00:30, 21 May 2010 (UTC)

While individual doctors and lab techs may well be competent and want to do a good job, the management of the company may work against them. For example, if a test requires 10 minutes to perform competently, but their management threatens to fire them if they take more than 5 minutes on each, then they have the choice of rushing each and doing a half-assed job, doing half of them properly and just faking the results on the other half, or being fired and replaced by someone else who will do one of those things. If a company is only concerned with short-term profits, this type of management pressure is a real concern. StuRat (talk) 14:32, 21 May 2010 (UTC)

I agree that individual consumers may well be nut-jobs, but the consensus of the whole should nonetheless be useful info, much like individual purchasers of stocks are often idiots, but nonetheless the stock market, in total, does a good job determining the long term value of companies, perhaps better than professional rating agencies, specifically when the effect of bribery is considered. While any small group can be bribed, or perhaps just cover up a problem that would otherwise "bring disrepute into our field", there's no way a large cross section of consumers can be bribed or act against their own interests. StuRat (talk) 14:23, 21 May 2010 (UTC)

I agree with Mr. 77.86: send your blood to two labs (or more, if you really want to be sure) and compare the results against each other. If they match reasonably well, then it's likely that they actually did some sort of test. Buddy431 (talk) 05:06, 21 May 2010 (UTC)

See http://www.bloodbook.com/ and click on "ABOUT US". -- Wavelength (talk) 05:48, 21 May 2010 (UTC)

Lab statistics

OK, let me ask another way. See chart:

Lab name      % of results within 10%
============  =======================
ABC Lab       93%
Quack Labs    12%
XYZ Labs      98%

Is there a place where I can get results like this ? Better yet would be a break down of how accurate each individual test is when performed at the various labs. StuRat (talk) 14:52, 21 May 2010 (UTC)

... Within 10% of what? Presumably, you mean some kind of gold-standard, trustable set of ideal and perfect measurements from a reliable laboratory. But who verified that set of results? (Presumably they are compared against another, "platinum-standard", ultra-trustable laboratory?) As you can see, the problem boils down to a degree of trust and verification. Web of trust describes a decentralized trust model - you can see that the problem has been thought about - but at some level, you must accept somebody on good faith alone - unless you can create and administer every part of the test individually. Nimur (talk) 15:49, 21 May 2010 (UTC)

Within 10% of the actual value. For example, if they are giving an RBC count, there should be an actual correct number of red blood cells. How do you determine what it is ? Taking an average of the lab results from many labs would work, possibly tossing out the values farthest from the average. StuRat (talk) 03:43, 22 May 2010 (UTC)

I can't be bothered to reply in different parts of this thread so I'll just post my reply down here.

"Hmmm, knowing "how much of everything should be in the blood of someone in the condition" could easily lead to faking the results, a true blind test would be better, in my opinion."

This simply is not possible. How can you define what is normal with a blind test? You need to establish what is normal based on average test results over time. You can't just take a blood sample and go "ooh looks a bit busy here with respect to leukocytes" -- you have to know how many leukocytes should be in the blood for a person in that condition! Bottom line, you need benchmarks to compare results against, otherwise you're just staring at a number which means nothing!

I completely disagree. The lab should not be given any clues as to what values are expected, they should just report the levels they find, and the doctor and/or patient can then decide if that's normal for them or a cause for concern. StuRat (talk) 04:01, 22 May 2010 (UTC)

You're bypassing the point entirely. How does that doctor know what's normal if the normal lab values haven't been calculated, let alone the patient. It's not possible to be given a figure out of a test and know if it's normal unless you have an average to compare it with. Without the average, you're looking at a meaningless number. It's that simple. Regards, --—Cyclonenim | Chat  00:01, 23 May 2010 (UTC)

I just don't understand your point at all. Going back to the RBC count example, why wouldn't a doctor be able to find out the proper range for a patient based on age and gender ? Why would you think the lab that does the test is the only source of such info ? Any patient with access to the Internet ought to be able to find that out, too, although perhaps relying on their doc is more reliable. StuRat (talk) 16:56, 23 May 2010 (UTC)

I don't mean that the lab is the only source of information; I mean that the labs have to get that information from somewhere. If you don't trust individual labs, why would corruption be any less prevalent higher up? What I'm saying is that if you question the authenticity of data that the labs use, then why would you trust where they get the information from? Every test has a reference range, which are based on literally hundreds or thousands of tests. Every lab will then use that reference range. If you're inherently distrusting the labs, then by definition you're also questioning the people who did the reference range average because that's the only information used in distinguishing patient's conditions based on lab values. All the references ranges are worked out with lots of time and effort, and accuracy! These are then used in the labs by every biomedical scientist. The only way the values given to doctors could be different is if, as you mention below, they are corrupt or murderous and trying to kill or harm the patient. To accuse a lab scientist or doctor of this is no different than questioning, say, a fireman for not putting out a fire because it'd cost too much! It's illogical, sure it might happen, but the chance of it happening is so slim that it doesn't warrant a whole study to analyse lab accuracy--especially when all labs are going to have the SAME accuracy based on those reference ranges. I don't know how else to explain that. Regards, --—Cyclonenim | Chat  19:23, 23 May 2010 (UTC)

The problem with giving the lab the patient info is that they could then use that to convincing fake the test results, or perhaps it might just weight their test results in the expected direction. Both are undesirable. Test results should not be biased in any way by the expected outcomes. Also, you argued that if a lab was doing something like this, eventually a large number of patients would be harmed and there would be an investigation. While I have no doubt that this is true, I'd like to prevent the large number of patients being harmed by having the oversight in place to catch such labs earlier on in the process, say by occasionally having other labs double check their results. StuRat (talk) 22:25, 24 May 2010 (UTC)

I agree that "the likelihood of them being hell-bent for corruption is very slim", but they don't need to be to give bad results. Let's start with the scenario of the lab management demanding more tests be performed by lab techs than they can do competently in the time allotted. Perhaps one lab tech notices that he could make his quota if he would occasionally skip a quality check phase of the test. Perhaps another lab tech notices and starts doing the same. A third might notice and complain to management, which might not take any action, but continue to give bad reviews to the 3rd tech for not meeting his quotas. Eventually everyone in the lab will be skipping the quality test. Then maybe one of them goes to work in another lab and tells them how the old lab skips the verification phase and never got in any trouble. This lab wants to be able to compete on time and price, so does the same. Eventually skipping the quality control can become the industry standard, in this way. Mechanisms like this can lead to a steady erosion of quality. It's only punishment for such actions that has the ability to stop it, provided the punishment is greater than the benefits of skipping the quality test. StuRat (talk) 22:46, 24 May 2010 (UTC)

But you're still assuming the problem exists in the first place. So far you've put forward no actual proof that labs are knowingly and purposefully producing inaccurate results to cut costs. I have no doubt there is pressure to cut costs, but I don't think people would sacrifice accuracy of tests for fear of lawsuits (a problem very existent in the US). You're making it sound, with statements like "you'd like to prevent the large number of people being harmed", that lab reports are new and it's your responsibility to make sure they go well. Instead, lab reports have been going for tens of years and no problems have been established as of yet. That time period is long enough to notice any significant inaccuracies, and science and bureaucracy are harsh mistresses: the one that fucks around will get caught out by the other. If bureaucracy cuts costs and forces scientific officials to make inaccurate results, scientists have a tendency to make those pressures very public in order to fix things. If science starts messing around with budgets and wasting money, governments will step in and impose cuts. It's a careful equilibrium and without statistics to back it up, I'm not willing to accept that the labs I've seen first hand are breaking rules and putting people's health at risk. As I'm in the UK there is even more pressure on labs, because finance is something the NHS lacks significantly. There are always targets and cuts in place, but I know for a fact not even the government dares to cut public spending in places where it will harm patients directly. Regards, --—Cyclonenim | Chat  12:44, 25 May 2010 (UTC)

"We seem to have a fundamental difference, you inherently trust everyone until (you become aware that) they have violated that trust, whereas I don't trust anyone or anything until they prove they are trustworthy. I sure hope you don't give your bank account numbers to "rich Nigerian princes" who e-mail you that they want to deposit money in your account. :-)"

The difference is that these rich Nigerian princes are people who lack any credentials whatsoever _{and usually have Yahoo! mail accounts!} The doctors and lab scientists are trained and are there in your best interest for the most part. To inherently distrust them seems silly when 99.999% of the time they're working with your best interest at heart.

99.999% ? Really ? You only think maybe 1 in 100,000 people would ever take a short cut that's not in the best interest of the customer ? I believe more than that many will be actual murderers, based on statistics and my assumption that lab techs are just as susceptible to human failings as any other person. I'd guess at least 1 in 10 would take occasional shortcuts. Your estimate seems absurdly low. I sure wish there was a way we could tell for sure, but that's rather the whole point of my question, isn't it ? StuRat (talk) 03:56, 22 May 2010 (UTC)

You know as well as I do that number wasn't literal. The problem is you're treating doctors like shopkeepers. In the US your doctors are funded by patient treatment costs recuperated by the insurers. Why would they cut corners? It's an incredibly illogical assumption because all these doctors and lab assistants are trying to help, and even if they are in it for the money, getting a correct lab value is still in their best interest. 1) It makes them less liable in a lawsuit should the situation of the patient become worse, or they die. 2) It allows for correct diagnosis of the problem: if they are well, they are discharged and no more money is spent. If they are ill, more expensive treatments are conducted and everyone still gets paid by the insurers or the government. You are yet to produce a logical reason to mistrust these officials, all I can see here is a trust issue. Mentioning that these lab assistants and doctors are murders is way more absurd that my natural trust of them! I very much doubt 1 in 100,000 doctors/lab assistants are murderers, and if you're going to make that sort of claim then it needs to be backed up. You mention statistics, but I see nothing but a little table you made up figures for. Regards, --—Cyclonenim | Chat  00:01, 23 May 2010 (UTC)

Here's an article where a former insurance company exec admits to many of the unethical practices they used to cut costs: [6] (I saw an even better TV documentary where a female exec admitted to denying legit claims, knowing it would cause deaths). With those in mind, do you really think it's completely impossible that such a company would also put so much financial pressure on the labs to do the tests cheaply that the labs would need to cut corners to meet those targets ? Then there's my brother's lab which obviously takes a shortcut that adversely affect test results, in not keeping samples frozen which are clearly marked "MUST BE KEPT FROZEN". As for the murder rate being above 1 in 100,000, it generally runs around 1 in 10,000 for all people. What makes you think that doctors and lab techs are somehow immune to having the same human nature as everyone else ? A medical degree or a certification doesn't make you into a perfect machine, as you seem to be arguing. More generally, the argument that "they are the professionals, so we shouldn't question them" has caused severe problems in many other fields, from trusting bankers to self-regulate our financial institutions and oil companies to self-regulate off-shore oil drilling, that the idea of blind trust in "experts" has been thoroughly discredited. Greed often causes them to do risky things which later result in disaster. StuRat (talk) 17:21, 23 May 2010 (UTC)

Human beings are indeed corrupt, sometimes. I'm not saying that every single medical practitioner is heaven-sent because that clearly isn't true, but I am saying that the likelihood of them being hell-bent for corruption is very slim. If you inherently distrust these officials, do you also distrust police officers, who have been known to be corrupt from time to time (dare I say more often than healthcare officials) ? Yes, corruption happens, but to assume it's happening is a different thing altogether. Any accuracy problems in labs would be brought to light under investigations when significant numbers of patients are affected. If the lab hasn't been brought under questioning, the chances are that it's not cutting corners, or at least not sufficiently to damage the main purpose: saving patients lives. If you know of specific examples, like your brother's lab, then the lab should be reported so the problem can be brought to light and fixed. Regards, --—Cyclonenim | Chat  19:23, 23 May 2010 (UTC)

Yes, I do mistrust police officers, and firemen, too. I have a healthy mistrust of anyone in authority. There should be oversight of all such people and organizations. It's the lack of oversight which causes corruption. Moving back to the financial institutions example, the credit card companies were basically honest until Providian started cheating people right and left, and suffered no serious consequences while making money hand over fist. This then inspired the rest of the credit card companies to cheat people too. Had Providian been smacked down early and hard, many of the abuses of the credit card industry could have been avoided. Instead they weren't punished for years, during which time the other credit card companies replicated all of their worst practices. StuRat (talk) 22:12, 24 May 2010 (UTC)

But Providian were a publicly held company, an actively for-profit company who clearly has no intention of helping people. Whilst the labs in the US may be owned publicly, too, I doubt they're willing to undergo many a lawsuit for inaccuracy in labs (which they would, if the problem existed, because people would die!) Regards, --—Cyclonenim | Chat  19:29, 25 May 2010 (UTC)

The problem with your little chart is that the chances are all of those labs are using very similar, if not identical, procedures, and so assuming fully competent lab scientists, they're all going to be around the high 98-99% range. ALL TESTS have a degree of error, it's called the standard error, but the vast majority of tests in hospitals have such a small degree of error involved that the results are almost always perfect. I'd venture to say you are probably in a small minority for distrusting inherently these officials, and I doubt there are any statistics on specific lab accuracy because they're all going to be roughly the same. Regards, --—Cyclonenim | Chat  16:28, 21 May 2010 (UTC)

If all the labs come out with about the same accuracy, that would still be valuable info that I'd love to see. StuRat (talk) 03:45, 22 May 2010 (UTC)

[Cyclonenim, please see wikt:inherit and wikt:inherent. -- Wavelength (talk) 16:44, 21 May 2010 (UTC)]

Argh, sorry. I'm usually such a pedant for vocabulary and grammar, too. Blame the 40 hours without sleep. Regards, --—Cyclonenim | Chat  17:46, 21 May 2010 (UTC)

I did a Google search for blood test accuracy, and found HowStuffWorks Videos "Accuracy in Blood Test Data" (14:02) by World Business Review on the topic "Blood Test Data Management". Wikipedia does not yet have an article specifically about blood test data management, but that expression can be useful in further searches on the World Wide Web. -- Wavelength (talk) 17:35, 21 May 2010 (UTC)

Breathing in Helium

Why does breathing in helium cause the human voice to become squeakier? I've gone through some websites on the matter, and they all say that it's because the speed of sound in helium is greater than in air, but I'm a little unsatisfied with this. It's not really an explanation; I still can't "see" why helium produces this effect. I figure that there are specific resonance frequencies in our voice box, and that changing the speed of sound in the voice box will change the resonance frequencies, but I'm at a loss as to why the frequencies will be shifted upwards with an increase in the speed of sound. Can anyone give a better description of what's happening? 173.179.59.66 (talk) 19:03, 20 May 2010 (UTC)

The shape of the larynx determines the wavelength of the sound. The vibrations aren't produced by the tissue in the larynx itself vibrating (as in a guitar string), but rather by allowing the air to vibrate within the space it creates (as in an organ pipe). That's why you won't get any vibration without air flow. Higher speed of sound with the same wavelength means higher frequency. Rckrone (talk) 19:28, 20 May 2010 (UTC)

What I said seems to be contradicted by the vocal folds article, so to be honest I'm a bit confused about this myself. The resonant frequency of the vocal folds should not depend on the type of gas that's next to them. Rckrone (talk) 19:42, 20 May 2010 (UTC)

First of all, here's a nice thing on speed-of-sound calculations and the Straight Dope relevant article. Taking in helium puts some of the gas in your vocal tract which does mean the speed of sound is faster. However, the difference in pitch should come about more when the sound leaves your mouth (which may be why, and I'M NOT AN EXPERT ON ACOUSTICS, you don't hear yourself with a high voice as much as others do). Your vocal cords vibrate with the same frequency and the energy of the wave should stay the same which gives it a longer wavelength, so when it transitions to the slower speed of normal air, that's when the frequency of the sound wave increases, resulting in an overall higher pitch. This is what I think occurs.

The relevant equation, by the way, is c=f*L, or the speed of sound equals frequency times wavelength, and E~c*f, or energy is proportional to speed of sound times frequency. When energy stays equal but the speed of sound drops between helium and air, the frequency must increase (energy is conserved). SamuelRiv (talk) 19:36, 20 May 2010 (UTC)

... so if you listened in helium, everyone speaking in air would have a deep voice? The "Straight Dope" article sounds confused to me. I think they mean that helium doesn't change the wavelength of the sound, but I'm not an expert on acoustics either, so I'm confused too! Does anyone know the truth? Dbfirs 00:01, 21 May 2010 (UTC)

No, you don't hear wavelength, you hear frequency. (At least, assuming you don't have helium in your cochlea; not sure offhand how that would affect things.) When sound of a given frequency crosses the air/helium interface, its frequency stays the same but its wavelength changes.

On the other hand, you generate sound of a given wavelength, because it's related to the geometry of the resonating chamber. --Trovatore (talk) 00:08, 21 May 2010 (UTC)

Ah, the article says the cochlea is "filled with a watery fluid". If that were replaced by helium, my guess is that you would go totally deaf, and the question would be moot. --Trovatore (talk) 00:10, 21 May 2010 (UTC)

... I was questioning the change in frequency at a boundary between gases, so helium in middle ear would be adequate to test SamuelRiv's theory. Dbfirs 00:17, 23 May 2010 (UTC)

Ah, let me state this clearly then: The frequency does not change at a boundary between gases. Well, barring some nonlinear effects such as second-harmonic generation, which I feel comfortable in saying have nothing to do with the effect of helium on your voice. --Trovatore (talk) 01:09, 23 May 2010 (UTC)

Thanks, that's what I was hoping someone would say with authority (and you did say it above, but thanks for emphasising it). Dbfirs 11:15, 23 May 2010 (UTC)

So my understanding is that the wavelength of emitted sound doesn't change when breathing in helium, meaning that the frequency emitted is higher. But then why isn't the pitch of the sound affected? 173.179.59.66 (talk) 01:56, 21 May 2010 (UTC)

The pitch is effected... your voice sounds higher! The speed of a wave equals it's frequency times it's wavelength. Since the wavelength remains the same, and clearly the speed remains the same, then it must be the frequency that changes (a.k.a. the pitch?) Regards, --—Cyclonenim | Chat  02:11, 21 May 2010 (UTC)

Except that most articles that I've read suggest that it is the timbre of the sound which is affected, rather than the pitch. 173.179.59.66 (talk) 02:31, 21 May 2010 (UTC)

I'd say it's quite clearly not timbre in it's official definition. Timbre is just the quality a specific note has, so if you play a guitar you can play the same note on the fifth fret of the A string and the twelfth fret of the D string, and the pitch is the same, it just sounds ever so slightly different. Pitch is another thing entirely and relates to the distance between the peaks in a wave, and is responsible for different notes. When you inhale helium, it's not just the quality of the sound you produce that changes, it's the pitch/notes you produce. Regards, --—Cyclonenim | Chat  03:33, 21 May 2010 (UTC)

I don't think the speed remains the same, not exactly the same anyway. We probably have an article on the speed of sound that explains what determines it. If I remember correctly, the effect of the mass density cancels out, but there's a difference between monatomic and diatomic media. --Trovatore (talk) 02:17, 21 May 2010 (UTC)

Don't get confused by timbre. You have to remember that the sound produced by any natural source will normally be a combination of more than one simple frequency. A change in frequency/wavelength (whatever we decided it was) will certainly affect the timbre. But the more obvious change will be in the pitch (which is just the frequency most prominent in our hearing of the tone).--Jabberwalkee (talk) 03:47, 21 May 2010 (UTC)

So are you saying that the pitch will change? That seems to contradict the Straight Dope article listed above, the author of which was fairly adamant that pitch is unaltered (he has several audio files to support his claims, although admittedly I thought the pitch did change). Likewise, Wikipedia's article on helium states that pitch is unaffected. 173.179.59.66 (talk) 04:06, 21 May 2010 (UTC)

The only thing that is guaranteed to (almost) stay constant is energy, as I stated before, and the sources I linked did not address this fact directly. The frequency with which your vocal folds vibrate determines the base frequency with which sound is emitted, and the associated energy can be used to determine the wavelength given the speed of sound. So if, as we know, energy stays the same but the medium of the sound wave changes to one with a lower propagation speed (speed of sound in air is about 1/3 of that in helium), then either wavelength must decrease or frequency must increase or both. In all except the most controlled thermodynamic environments, both will occur, and more detailed calculations can predict the ratio with which they change - it certainly depends on the interface between going from air with a lot of helium to air with virtually zero helium. Point is that frequency definitely increases, so pitch increases. SamuelRiv (talk) 07:27, 21 May 2010 (UTC)

No no no. Energy isn't going to help you. Energy gets dissipated; energy gets reflected from the interface. Energy is absolutely not the right thing to consider here.

The important things to think about are frequency and wavelength. The relationship between frequency and wavelength is controlled by the speed of sound in the medium, in an obvious way (the wavelength is the distance along one full cycle; the frequency is the reciprocal of the time that one full cycle takes; work it out from there). Energy is a distraction; you might be able to rephrase things in terms of energy somehow, but I don't see the point.

As I said above, what you hear is frequency, not wavelength. So the question is, which, if either, remains constant when you do the same thing with your vocal apparatus with a breath of air, as opposed to helium.

As someone said above, the vocal folds, which drive the whole thing, should not be affected much by the helium — they should put out the same spectrum of frequencies (not wavelengths) in either environment.

However, the way your resonating cavity responds to the driving from the vocal folds, is controlled by wavelength. It's a question of which wavelengths fit nicely into the cavity. So if the vocal folds drive the resonance with a noisy spectrum, some of the frequencies will be selected and some will not, and this depends on their wavelengths. --Trovatore (talk) 18:18, 21 May 2010 (UTC)

I would have thought that the same wavelengths get "selected" regardless of medium the sound is propagating in, because the resonance wavelengths are dependent on the geometry of the vocal tract alone. Then, if the speed of sound is greater helium, by the relationship f = c/λ the frequency must increase as well, resulting in a higher pitch. However, several sources have stated that pitch doesn't change, but personally, based on the reasoning given above as well as my own experiences with helium, I would have to disagree with their assessment. 173.179.59.66 (talk) 20:02, 21 May 2010 (UTC)

Trovatore is on the right track. The human vocal tract has four major resonance spaces of different dimensions. Assuming your larnyx remains in its usual place and you form the usual vowel shapes with your mouth, tongue, and soft palate then they will resonate at normal their wavelengths (or higher frequencies), but the pressure sawtooth wave pulse train generated by the opening and closing of the vocal folds will be at a fundamental frequency that is close to normal. The harmonic series of overtones above that fundamental will be at near normal frequencies, but the specific harmonics that resonate in each of the cavities will be those close to the (now temporarily higher) natural frequency of those cavities. LeadSongDog come howl! 19:58, 21 May 2010 (UTC)

To be perfectly honest I didn't really understand your explanation. Here's what I got from it: 1) the resonant wavelenghts of sound in the vocal tract will be the same; and 2)The frequency of the sound produced from the vocal flaps will be roughly the same. The rest about the harmonics confused me a bit. My (apparently flawed) understanding of what was happening was something like this: air produced from the lungs travels through the vocal folds, producing sound waves at a variety of frequencies. These sound waves then entered the vocal tract, where certain wavelengths (and hence certain frequencies) were selected by resonance, depending on what sound the speaker wished to make. My impression from what you said is that the sound from the vocal tract and from the vocal folds independly contribute to the final sound quality, but I'm not sure. Maybe if you showed me where my picture is wrong I would be able to finally understand what's going on. 173.179.59.66 (talk) 05:47, 22 May 2010 (UTC)

Could someone with appropriate facilities please test the conflicting theories by filling an organ pipe with helium, and playing a stringed instrument in helium? Surely someone, somewhere in the world, has tried this? We could test out the frequency versus timbre argument if someone could record themselves saying the same thing in air & in helium, then we could examine and compare the waveforms. I still think that "Straight Dope" is wrong. Dbfirs 00:00, 23 May 2010 (UTC)

Let me see if I can summarize what LeadSongDog is saying, which may also clear up Dbfirs' question. I'm assuming he's correct that the driving is via a sawtooth function, one that looks like

          /|   /|   /|   /
         / |  / |  / |  /
        /  | /  | /  | /
       /   |/   |/   |/

where what's being graphed here is pressure agaist time, or rather the pressure wave that the vocal folds would generate if they were not in the resonant chamber.

According to our article, the Fourier series of this function falls off as 1/k, where k is frequency. So maybe its Fourier transform looks something like this:

      *
      *
      *
      *        *     
      *        *       *
      *        *       *      *

where the horizontal axis is now frequency rather than time. This means that the signal breaks up into a collection of discrete frequencies, weighted by different amounts.

Now, when you add the resonant chamber, some frequencies produce constructive interference and are enhanced; some produce destructive interference and are diminished. So maybe in air, the Fourier transform now looks like this instead:

               *
               *
               *     
      *        *       *
      *        *       *      *

because maybe the second frequency is close to the natural frequency of the resonating chamber.

Now suppose you're breathing a light gas instead, some heliox mixture, and the speed of sound is higher, lets say twice as fast. That means the wavelength of the third harmonic (the fourth column) is now the same as the wavelength that the second column had in the above picture, and therefore it's the one favored, whereas the others are diminished. So now maybe it looks like:

                              *
                              * 
               *       *      *
      *        *       *      *

or something like that.

Note that the component frequencies have not changed; only the proportions with which they are mixed has changed. The fundamental frequency is the same, which may be what Unca Cecil meant. However the peak frequency, the one with the greatest amplitude, is now twice as high, so if you consider that to be the "real" pitch, then you'll say it's higher. But if you go by pitch equals fundamental frequency, then indeed the pitch has not changed, only the timbre.

This is an off-the-cuff example and I don't know if the quantitative parts are realistic. But I gather this is the general idea. --Trovatore (talk) 01:42, 23 May 2010 (UTC)

Okat I think I get it. So basically, the human ear measures pitch by the harmonics involved, not by their relative strength (which is what produces timbre), right? 173.179.59.66 (talk) 01:55, 23 May 2010 (UTC)

Like a violin sounds "higher" than a bassoon when they are playing the same note? Also, are you saying that a stringed instrument will sound exactly the same if played in helium, but an organ pipe will sound squeaky because of high harmonics? Dbfirs 11:07, 23 May 2010 (UTC)

A solid-body electric guitar will sound the same in helium or air, as gas plays no part in its sound production. A hollow body, such as a cello, will sound different, taking on a timbre more like that of a violin in air. An organ pipe is not harmonically rich, it simply resonates at its fundamental pitch. It would sound higher in helium simply because of the change in that fundamental pitch. LeadSongDog come howl! 21:39, 24 May 2010 (UTC)

Natural undersea oil spills

The oil leak in the Gulf is apparently a major ecological disaster, resulting from a relatively tiny opening to the seafloor from an oil deposit below the sea. Are these oil deposits immune to natural processes which could create an opening, such as an earthquake creating a fracture which allows flow up into the ocean, or a volcano which fractures the thick rock dome above the oil? Do geologists find evidence that there has ever been a significant natural undersea oil leak? Even in ancient times, people found natural seeps on dry land. Wouldn't there be similar underwater oil seeps of varying flow rates? Edison (talk) 19:10, 20 May 2010 (UTC)

Yes. Oil does ooze naturally from shallow deposits as this article discusses - and it doesn't take a volcano or even an earthquake to make that happen. There are plenty of places up on dry land where this happens too (See La Brea Tar Pits, for example) - humans have been scooping the stuff up and using it for thousands of years (See Oil_industry#Early_history). Although the magnitude of this seepage is tiny because the pressures are so small. In the gulf right now, you have to understand that the drilling rig had bored down through 18,000 feet of rock below the 5,000 feet of water. So the likelyhood of oil coming through all that rock in that area naturally is pretty slim! But the weight of 18,000 feet of rock pushing down on the oil - means that it is squirting upwards with tremendous pressure. Our article on the oil spill points out that the total oil reserves at that site are 50 million barrels...but if it's really coming out at 100,000 barrels a day - as some are estimating - that reserve is shrinking noticably! SteveBaker (talk) 20:27, 20 May 2010 (UTC)

See Tarball (oil) - some of the refs mak it clear that these are found naturally as well as man made

eg http://pubs.usgs.gov/of/2009/1225/ (unfortunately searching for "tarball" in the oil sense is difficult - due to computer usage of the term.) I've heard of them before and believe them to be well known to beachcombers.77.86.115.45 (talk) 21:14, 20 May 2010 (UTC)

(ec)See also Asphalt volcano for an example of a past natural underwater oil seep. People involved with exploring for hydrocarbons make use of satellite photos to identify natural oil slicks from such underwater seeps to show that there is a working source rock down there. They have to do repeat surveys, of course, to try and remove the unnatural ones (ships cleaning tanks etc.). Mikenorton (talk) 21:16, 20 May 2010 (UTC)

newtonian fluids

Is Mercury a newtonian fluid —Preceding unsigned comment added by 82.201.241.168 (talk) 21:35, 20 May 2010 (UTC)

on the whole yes [7] 77.86.115.45 (talk) 21:43, 20 May 2010 (UTC)

Biomedical control systems

hello i am searching for an application of the control systems in the biomedical field but i'm stuck and i cannot get all what i want, it must have block diagram and meaningful description,,,,,any one could help me?? —Preceding unsigned comment added by 41.196.197.43 (talk) 22:04, 20 May 2010 (UTC)

You need to be a little more specific. Manufactoring control systems, or control systems pertaining to regulations? Regards, --—Cyclonenim | Chat  22:15, 20 May 2010 (UTC)

Publishing scientific literature.

I just have a few questions about publishing research.

1. ) How is it decided what journal any piece of scientific research will get published in? Does the research team just pick one they think is the most suitable? I've heard reference to top tier, and 2nd and 3rd tier journals.
2. ) Is there a process to decide which tier they will try to be published in? Surely no one says "my research is pretty dodgy, I'll try to publish in 3rd tier"?
3. ) What happens if a paper is not accepted for publishing? Are there costs involved in submitting a paper to a journal if it is rejected?
4. ) Can you just keep trying less and less reputable journals until you hit one that will publish your research?
5. ) Is there some place where these kind of introductory questions to this subject are addressed? I've read the Academic publishing and Scientific literature but they don't really cover these "idiots guide to publishing scientific literature" kinds of questions. Vespine (talk) 23:15, 20 May 2010 (UTC)

The researchers (or institution) submits a paper to the journal of their choice - in general they will pick one that is applicable, some are more prestigious than others, some are more "technical" than "theoretical" etc. The submitted paper is reviewed before publishing by the publisher, and other researchers. Peer review is key here. I'm not aware of charges for submission of papers - most journals publish the rules of submission online eg [8]. Yes you can keep trying until someone accepts it...(better if you know your limits at the start) Last question - probably a good way would be to pick a journal, and look up their submittence method online - should give a good idea of the method if not the practice.. Another good way would be to ask here :) I anticipate many other people will be able to give much more insight into the process here. (oh.. you often need a referee to support your submittal of a paper to a journal - usually someone old and well respected in the field etc ... or at least the department you work in will exert some control over what you put forward for publishing - they don't want you submitting any old tat and giving them a bad name .. etc .. this probably varies a lot from place to place) 77.86.115.45 (talk) 23:26, 20 May 2010 (UTC)

eg here are some of the info pages for Angewandte Chemie specifically to do with how referees judge the article and decide if it's recommended for acceptance [9] . I'm not sure about tiers - (don't think they are 'official') - but see Impact factor . Was there any field you were thinking of in particular? 77.86.115.45 (talk) 23:37, 20 May 2010 (UTC)

In general: 1. when you are in a field, you know what kind of article will work with what kind of journal. You know which articles of yours are worth sending off to Nature and you learn which ones go in Proceedings of a Very Limited Subfield of My Discipline. Tiers generally reference the size of the audience and likelihood of future citation ("impact factor")—Nature and Science are at the top because basically all scientists read them and cite them. 2. It's less of a "my research is dodgy" calculation than a "will these editors be interested in my paper" calculation. "Is this paper sufficiently interesting/important to get into the biggest and best?" is the sort of calculation made. The comment above regarding some journals being more specialized in different ways or for different audiences (e.g. more theoretical, more technical, etc.) is correct as well. 3. There are no costs to being rejected born by the submitters other than time. There are costs in terms of time of reviewers. There are a number of ways you can be rejected—from flat out rejection to "revise and resubmit" requests. 4. Yes, but it does take time to submit things, and getting a reputation for this sort of thing is probably not ideal. 5. Advisors, generally speaking. An advisor (at a university) in a given field usually knows the landscape of that particular field and tells their students how it works. It is slightly different for every particular field (they have their own norms, their own idea of which journals accept which types of articles, etc.). --Mr.98 (talk) 03:21, 21 May 2010 (UTC)

Note that if you submit research in a given field, the number of experts able to review it is limited, and, by the birthday paradox, there is a good chance that the same reviewer will get your paper again. In that case it should really show that you took his previous comments into account, or your reputation will suffer. I've put together a number of workshop programs and journal issues, and I once had a comment from a reviewer that yes, he can review a certain paper easily, as he already had rejected it 4 times. This is not good for the chances of the paper or the author... --Stephan Schulz (talk) 12:42, 21 May 2010 (UTC)

It is not generally the case that the reviewer will "hold a grudge" against a paper he has reviewed before for the same (or a different) journal. More than once I reviewed a manuscript for a journal and cited the shortcomings in the research (such as potential confounds) or its presentation (such as alternative explanations for the results). The researcher did additional experiments(to rule out confounds), and added additional explanations of procedural details to remove ambiguity, and then I recommended acceptance of the manuscript. In the end, the work became a much-cited article. The funny part is that the writer may be an important, distinguished and well known figure in the field, and the anonymous reviewer may be a lowly grad student, yet the researcher has to jump through hoops to satisfy the reviewer's objections. The researcher will typically try again with the more important journal, correcting the flaws (or pointing out the idiocy of the objections) rather than shopping the manuscript to lesser journals, since the prestige of the journal is important in getting tenure or getting a grant renewed. This is probably different from a writer of a piece of fiction, since the fiction writer might have an "artistic vision" which he would not want to compromise, just as a painter might not want to add paint to his canvas to satisfy a critic and get into a particular exhibition. Edison (talk) 15:10, 21 May 2010 (UTC)

There are generally no monetary costs for submitting to most scientific journals. (Some do charge for the paper to be published, open-access journals for example.) The main cost when submitting a paper for publication is temporal. Getting it reviewed, fixing/touching up/totally redoing what reviewers point out might take a lot of time. Also, flat out rejection means you have to try for another journal (Note: you can not submit the same paper to multiple journals at the same time) trying for another journal is starting over time-wise. Most researchers don't want to waste time doing this, so they generally submit to the "best" journal that is appropriate that they also except to have a good probability of being accepted. --Rajah (talk) 05:17, 22 May 2010 (UTC)

Even distinguished journals commonly have "page charges" and may charge to print an article sooner. Going down the pecking order to non prestigious journals, there are those which are vanity press and print any paper that is submitted, for a large fee. Edison (talk) 19:44, 22 May 2010 (UTC)

May 21

Absorbent glass mat (AGM)

can i get a Absorbent glass mat (AGM) battery 4 my honda accord —Preceding unsigned comment added by Tom12350 (talk • contribs) 04:16, 21 May 2010 (UTC)

It would probably be more expensive than an ordinary one, and you won't see much difference if it isn't a hybrid. --Chemicalinterest (talk) 15:37, 21 May 2010 (UTC)

Actually, quite a few modern non-hybrid cars use these batteries - they last longer and are both smaller and lighter than a regular car battery. So even on a non-electric car, they save energy just by making the car lighter. My car has one - on previous MINI Cooper'S models there was no space under the hood for the battery - so it had to go into the trunk - I was surprised not to find it there...and doubly surprised when I couldn't see it anywhere under the hood either! On my car, the amazingly tiny AGM battery is tucked away in an extremely hard-to-reach place (against the fire-wall right beneath the lower-right edge of the windscreen, hidden in the ducting and air-vent metalwork). The claim is that they are reliable enough to never need replacing...We'll see!

I don't see any reason why you shouldn't be able to replace a conventional battery with one of these gizmo's - weight savings are always a good thing! But it might be wise to check with your local Honda dealer before you do it...you never know what weird stuff is different with them. SteveBaker (talk) 20:19, 21 May 2010 (UTC)

Photon clocks in GR

According to the equivalence principal, in a uniform graviational field, clocks at different heights will run at different speeds. If two identical photon clocks (a clock consisting of two mirrors seperated by a fixed distance with a photon reflecting between the two to measure time) are placed at different heights, then it seems that they too must run at different rates. But this would seemingly imply that the speed of light changes with height, which is obviously not true. So what gives? 173.179.59.66 (talk) 08:02, 21 May 2010 (UTC)

I assume you mean at different heights in a spherically symmetric gravitational field (which is not uniform as the direction and strength of the field both vary). If you have two photon clocks at different heights then the curvature of spacetime is different and light travels along different geodesic paths within the two clocks - so you need to think about what you mean by "identical" photon clocks. Parallel transport may be a useful concept here. Gandalf61 (talk) 08:21, 21 May 2010 (UTC)

No, I meant a uniform gravitational field. 173.179.59.66 (talk) 16:58, 21 May 2010 (UTC)

Along with time dilation, you also have length contraction. So the distance between the two mirrors will be shorter in the clock in the stronger gravitational field. Ariel. (talk) 20:07, 21 May 2010 (UTC)

Are you sure you got that the right way round? Would not the stronger field be time dilated, compared to the weaker field, and therefore have a bigger mirror spacing to get the same time delay. You could get the same idea by measuring wavelength. Graeme Bartlett (talk) 20:55, 21 May 2010 (UTC)

And the gravitational fields are the same for both clocks, no? Unless you meant potential...173.179.59.66 (talk) 21:19, 21 May 2010 (UTC)

If you really do mean a uniform gravitational field then the two clocks are indeed equivalent and run at the same rate from the point of view of any observer. You will only get a difference in time dilation rates if the gravitational field is non-uniform. Gandalf61 (talk) 21:28, 21 May 2010 (UTC)

I have to disagree with you on that one. Replace the uniform gravitational field with a uniformly accelerating rocket, with a clock A at its front and a clock B at its tail. If clock A emits light pulses at a uniform rate, then the time it takes for any pulse to reach point B from point A will L/(c+v), were L is the distance between the two clocks (which remains constant). Because v increases , the pulses will take increasingly less and less time to reach clock B, so an observer at B will conclude that the clock at A is running faster. Equivalently, redshift still occurs in a uniform graviational field, so relative time dilation must necessarily still occur. 173.179.59.66 (talk) 05:32, 22 May 2010 (UTC)

You need to be clear about what you mean by "uniform acceleration". If your ship is a solid object with a rocket that accelerates the back at a constant rate, then the (constant) acceleration of the front of the ship is not the same as the (constant) acceleration of the back. This situation is often called "uniform acceleration", but the acceleration is not actually uniform, if "uniform" means "the same everywhere". You also have to be careful when you say that the distance between the clocks is constant. It's not constant with respect to any inertial reference frame. It's constant with respect to a Rindler frame, but that doesn't match the usual special relativistic definition of length. -- BenRG (talk) 01:45, 25 May 2010 (UTC)

It's not clear to me what a "uniform gravitational field" would be in general relativity. The closest thing is flat spacetime in Rindler coordinates, which is not uniform inasmuch as the acceleration needed to stay at the same (x,y,z) position varies as a function of x. Trying to apply length contraction and other concepts from special relativity to this problem is hopeless. (Length contraction barely makes sense in special relativity, in my opinion, but that's a different question. It makes even less sense in general relativity.) There's no difficulty in the definition of identical clocks as long as they're small compared to the scale of variation in the gravitational field (which is the usual assumption).

When people say that the clocks run at different rates, what they mean is that if you send periodic signals ("ticks") from the clocks to a common location, the received signal rate at that location will be different for the two clocks. This is the same as saying that there is gravitational redshift. Light clocks essentially define what time means at a given location, so you can't say that they run fast or slow in any absolute sense. If you do a local speed-of-light measuring experiment with a light clock and a meterstick, you'll get c. -- BenRG (talk) 22:23, 21 May 2010 (UTC)

I'm not very well aquainted with general relativity, but I'm using as an approximation a gravitational field equivalent to a uniformly accelerating rocket, which is simple enough so that I can understand with my current level of knowledge. In that case, two observers at different altitudes will the other's clock run slower or faster depending on the relative height of the observers.173.179.59.66 (talk) 05:37, 22 May 2010 (UTC)

Time dilation due to constant acceleration depends on rate of acceleration and initial velocity, but not on initial separation - see Time dilation#Time dilation at constant acceleration. Therefore, if your definition of "uniform gravitational field" is "equivalent to constant acceleration", then the time dilation in your "uniform gravitational field" will not depend on separation either. So all (stationary) clocks in this "uniform gravitational field" will run at the same rate. What makes you think they will not ? Gandalf61 (talk) 14:18, 22 May 2010 (UTC)

In the wikipedia article you linked to, the observer is outside the rocket, and so the time dilation in that case is just a special relativistic effect. In my scenario the observers are both inside the rocket. The thought experiment that I mentioned above shows how two clocks at different heights in an accelerating rocket will run at different rates. If you don't trust me, then here's a more comprehensive article: http://www.peaceone.net/basic/Feynman/V2%20Ch42.pdf173.179.59.66 (talk) 18:10, 22 May 2010 (UTC)

Feynman's observer is outside of the rocket too. For an accelerated observer inside the rocket, the lengths L1 and L2 would be the same. You need to have an observer outside of the rocket, in an inertial frame of reference, to establish a baseline time against which you measure proper time and hence calculate time dilation. Gandalf61 (talk) 16:11, 23 May 2010 (UTC)

Yeah, and this outside observer will see both clocks run at the same rate. But the observers inside the rocket will notice a discrepancy. 173.179.59.66 (talk) 04:27, 24 May 2010 (UTC)

Then you seem to have answered your own question. The true time dilation relative to an inertial frame of reference is the same at all points in the uniform gravitational field. The apparent time dilation observed by two stationary observers within the uniform gravitational field comparing their proper times, does depend on their separation, but this is a consequence of the fact that these observers are not using an inertial frame of reference. Gandalf61 (talk) 09:01, 24 May 2010 (UTC)

There's no "true" or "apparent" time dilation. There is only the results of various experiments. I'm still not sure what a "uniform gravitational field" is. You (Gandalf) seem to be talking about two ships accelerated by independent, identical rockets with one clock aboard each one. The anon is talking about one ship accelerated by a single rocket with two clocks on board. These are different physical situations. In Newtonian physics they would be equivalent, but relativistically they aren't. See also my reply above (the one dated today). -- BenRG (talk) 01:45, 25 May 2010 (UTC)

Note that in weak gravitational fields, the metric in natural units is approximately given by:

$ds^{2}=(1+2V)dt^{2}-(dx^{2}+dy^{2}+dz^{2})$

where V is the Newtonian gravitational potential. Count Iblis (talk) 17:08, 23 May 2010 (UTC)

Wind Turbine and surface drag

I read an article on a new paint that reduces wind resistance [10], and one of the applications mentioned was wind turbines. My first thought was that you would not want to reduce wind resistance on a turbine or the air would just slip by without turning it. Then I began to wonder whether the turbine is turned by a pressure difference rather than friction with the air, and if so does the creation of the pressure difference rely on friction? Even if the wind resistance is not responsible for the effect, is it in any way detrimental? I am now completely confused as to what actually makes a wind turbine turn! -- Q Chris (talk) 09:29, 21 May 2010 (UTC)

It depends on the type. Some wind turbines work by redirecting the air flow sideways, creating torque via Newton's third law. These usually have flat vanes angled into the wind. Most modern high-performance turbines have an airfoil profile and generate torque by the pressure difference caused by the different speeds of air travelling over the more curved leading side and the straighter trailing side. In either case, energy lost to friction just warms the blade and does not contribute to the generating capacity. --Stephan Schulz (talk) 09:40, 21 May 2010 (UTC)

Thanks Stephan. I can see that the energy that just heats the blades will not aid generation, but will it be detrimental to the generation? As far as I can see the air will be slipping off in the same direction that the blades rotate, so it won't make much difference either way. -- Q Chris (talk) 10:03, 21 May 2010 (UTC)

What friction will do is slow down the airflow. Thus, somewhat simplified, you have a reduced "effective wind". In the case of simple vanes, for example, the induced sideways motion of the downwind air will be less (part of the energy is lost to friction), and hence the opposing force acting to turn the vanes will be less. A similar argument can be made for the airfoil. --Stephan Schulz (talk) 11:33, 21 May 2010 (UTC)

Also, friction can result in turbulence, which can wiggle the blades and cause heating and wear and tear on the bearings. Thus, laminar flow is preferred. The blades themselves may also tend to get pitted more if grains of sand are dashed against them, due to turbulence. This could in turn cause more friction and turbulence, and also unbalance the blades. StuRat (talk) 15:05, 21 May 2010 (UTC)

What is this weird creature?

Opossum

Opossum

River otters

weird creature Kittybrewster ☎ 11:21, 21 May 2010 (UTC)

Here's some more pictures: [11]. Most of the comments (i.e. here) I've seen are saying otter or possum, or possibly a nutria or groundhog. Buddy431 (talk) 12:35, 21 May 2010 (UTC)

I vote for "exceptionally ugly/drowned looking opossum." Compare with this beauty queen. Either than or an otter whose lost a lot of fur on the snout. (The skull is very otter-like.) --Mr.98 (talk) 12:37, 21 May 2010 (UTC)

If it's 'playing possum' it's overdone it.. Really appears to 100% dead possum. cf image seach for "possum skull" - note the lower 'canine' - not otter as far as I know.

Does anyone know what happens to the hair - is it common for it to fall out of dead animals in water? eg this [12] 77.86.115.45 (talk) 16:29, 21 May 2010 (UTC)

The face looks like a wolverine's, but the article says "The creature's tail is like a rat's tail and it is a foot long.", which suggests possum. Maybe a hybrid? Wolverines don't have rat-like tails do they? Vranak (talk) 17:59, 21 May 2010 (UTC)

I'd vote for otter - perhaps with mange, perhaps something else - decomposition? - causing the fur loss. The face looks very otter-like to me, though I'm curious about the tail. Of course, if hair loss also occurred on the tail, it could well look like a rat tail. Matt Deres (talk) 19:39, 21 May 2010 (UTC)

I don't think anyone would look at an otter tail and say it was rat-like though. Vranak (talk) 19:51, 21 May 2010 (UTC)

Comparing to the pictures to the right (feel free to adjust the formatting, I can't figure it out), I think the snout is too short for an opossum, and the ears too small. Also, the place where the whiskers would be doesn't seem quite right either. I'm voting tentatively for the river otter. Perhaps without fur on the tail, someone who has not seen a rat recently would say it looked like a rat tail. The river otter's ears look closer to me, as does the snout and the whiskers. Falconus^{p t c} 21:03, 21 May 2010 (UTC)

Note: I revised inaccurate captions on the pictures. I am fairly sure, for example, that the bottom picture is not a badger, but rather a river otter.Falconus^{p t c} 22:06, 21 May 2010 (UTC)

Bovine Tubersulosis versus the Human Form.

During my research into my family history I've discovered that my grandfather lost three of his siblings over a 5 year period at the turn of the 20th. Century. I am wondering if occupation conveyed a part of the other siblings immunity? I know, for example the Jenner discovered that immunising someone with Cow Pox gave them a marked immunity to Smallpox, hence my curiousity regarding T.B.11:47, 21 May 2010 (UTC)~ —Preceding unsigned comment added by 2.102.26.59 (talk)

Assuming that contact with Mycobacterium bovis can generate resistance to Mycobacterium tuberculosis (the more typical cause of tuberculosis in humans), it is important to take a major difference between M. bovis and the cowpox virus into account: the latter doesn't cause a typically life-threatening disease, while the former does. This is what made inoculation so useful. – ClockworkSoul 16:55, 22 May 2010 (UTC)

0t,1t 2t bend test / galvanized/colour coated coils

Does anyone recognise what is being asked here Wikipedia:Reference_desk/Miscellaneous#Bend_test ? 77.86.115.45 (talk) 11:57, 21 May 2010 (UTC)

Oil spill - quick drying cement?

Why cannot the source of the oil spill just be covered with a large amount of quick drying cement. After the first batch has hardened, another batch, then another. This is not a silly question - cement does set under water. 92.28.253.142 (talk) 14:32, 21 May 2010 (UTC)

I believe the force of the oil, which is coming out under pressure, would push the concrete out of position before it could harden. StuRat (talk) 14:58, 21 May 2010 (UTC)

As do many polymers, going back to the wet-climate-set Chinese lacquer. My guess is that the big question is how to put a big heavy block onto a big hole spewing crud at very high pressure and not just having it get knocked to the side by the spray. Consider how hard it is to stop the water from coming out of a hose with your thumb. SamuelRiv (talk) 15:07, 21 May 2010 (UTC)

As an extension to the above idea - first cover the flow with large chunks of broken stone - so that the oil is diffused out between the gaps in the stone - the concrete would be less likely to be swept away before setting due to the reduced local flow rate.. In practice once completed the flow would probably just exit below the stone - and scour the (loose?) sea bed, creating its own channel.

I wonder if a rheopectic substance or Dilatant would help here (probably not).77.86.115.45 (talk) 16:13, 21 May 2010 (UTC)

Along these lines, Google for: bp oil "junk shot". DMacks (talk) 16:29, 21 May 2010 (UTC)

I wonder if they've considered using (hydraulic?) clamps to 'crimp' the end of the pipes to restrict the flow? - are the pipes made of a workable steel or a brittle steel?77.86.62.107 (talk) 16:57, 21 May 2010 (UTC)

Not a good idea, it could break the pipes. Even workable steel has a limit to which it could be cold-worked before it starts to crack (generally no more than 20% deformation), so "crimping" the pipes won't work. 67.170.215.166 (talk) 05:05, 22 May 2010 (UTC)

And is it possible that it is impossible to close this oil spill until all the oil has run out? Mr.K. (talk) 16:00, 21 May 2010 (UTC)

No, just until the pressure drops. Are they not planning to drill nearby to relieve the pressure? Dbfirs 17:19, 21 May 2010 (UTC)

"They" (we) are planning to do just that, but it could take up to several weeks due to the great depth of the well required and also the difficult rock formation. (Well, I don't know all the particulars -- I work on the refining end, not the extraction end -- but that sums up what I've heard from the company management.) FWiW 67.170.215.166 (talk) 05:00, 22 May 2010 (UTC)

I believe the amount of oil shooting out of the broken pipe would prohibit this sort of remedy. And it's a little sloppy too, just pouring heaps of cement over a leak. Reminds me of Chernobyl. And just getting the cement out in the middle of ocean, and then down miles beneath the surface, is rather more problematic than, say, trying to plug Old Faithful in the same manner. Which, come to think of it, seems rather problematic in itself. Mind you one is a pipe, the other, a natural geyser -- apples and oranges and all that. But the point remains, pouring cement at those depths, that far from land -- not entirely trivial. But ultimately, I feel that the force of the oil is the critical factor. From all I have read, pumping drilling mud into the aperture is the way to go. Vranak (talk) 17:50, 21 May 2010 (UTC)

If I understand it correctly, the advantage of injecting heavy mud is that it can flow down the borehole against the oil counterflow. As the depth of the borehole fills with mud it creates a backpressure to gradually reduce the oil flow while also narrowing the part of the borehole through which the oil is flowing. The other approach, of capping the pipe, can only work if the pressure inside the cap is kept below the surrounding water pressure. Given the amount of dissolved gas from this well, that's not a trivial thing either. As the gas rises and expands it undergoes adiabatic cooling (like the working fluid in a refrigerator or air conditioner). On mixing with water this cold gas can form ice crystals that clog the pipe to the surface platform. This appears to be what happened to the first attempted cap. LeadSongDog come howl! 19:31, 21 May 2010 (UTC)

Not exactly ice crystals but methane clathrate, which is less dense than pure water ice. The mud (it's actually synthetic) is made extra dense by adding the mineral barite to it, which is how highly pressured oil and gas are controlled when they are first encountered when drilling. Mikenorton (talk) 19:55, 21 May 2010 (UTC)

The key problem here is three-fold. One is pressure - the oil isn't just slowly washing out - it's coming out at some ungodly pressure. Below the seafloor, there is about 18,000 feet of solid rock pressing down on the oil reservoir - that's an incredible amount of pressure. Nothing like wet cement is going to be able to resist that. Second is temperature. This oil is incredibly hot. Third is that there is a lot of debris there - for starters, there is 5,000 feet of crumpled up pipe that fell from the rig onto the well-head. Then there is debris from the rig itself. So wet concrete is out of the question. Even dropping a very large concrete block onto the well-head won't work because the oil is under such pressure, it would just channel a route through the sand and stuff underneath it and squirt out around the edges. So you'd have not one neat little pipe to cap - but the entire perimeter of the concrete block. The various domes and such they've tried (and failed) with would have to have the oil continually sucked out of them - with a suction more powerful than the pressure of the oil - so as to 'suck' them onto the sea floor. These are all very difficult solutions.

The one I could imagine working would be to construct four vast rolls of flexible water/oil-proof fabric or plastic sheeting - each 5,000 feet long by (let's say) 100 feet wide - and to unroll these from the sides of ships to create four curtains around the well-head - then to heat-seal or 'zipper' the edges together as they are unrolled to make a vast, square-cross-section, floppy tube that could eventually rest on the seafloor far enough from the well head to avoid the debris field and the immediate heat/pressure of the oil. (You'd have to weight-down the bottom edge of each strip). This container would start to fill up with oil - which could then be pumped out from ships on the surface. The large width of the tube would ensure that the oil had room to expand and to relieve the pressure. Since oil is less dense than water, and we're pumping out the inside of this giant tube - any small leaks would have water flowing in - not oil flowing out. The technical difficulty is in handling such enormous amounts of fabric - and how well the stuff performs at the very low temperatures at the bottom of the ocean - also, how the pressure of ocean currents would work to push the thing out of shape.

SteveBaker (talk) 20:03, 21 May 2010 (UTC)

You're hired. Get your ass to the Gulf of Mexico. Comet Tuttle (talk) 20:16, 21 May 2010 (UTC)

Well, there's theory, then there's practice. I should think that Red Adair was so good at capping blowouts because of his experience in the field, not so much a sound theoretical background. I also imagine that too much theory and not enough experience was one of the chief causes for this mess in the first place. Vranak (talk) 20:20, 21 May 2010 (UTC)

The oil coming out now is actually at low pressure. It's being dumped into the ocean as quickly as the weight of the rock is able to force the oil into the well, and so there is very little accumulation of pressure. (Even given the large weight of the sea floor, oil will move slowly through the pore spaces in oil bearing rock.) If you are losing "only" 100,000 barrels per day through a 50 cm pipe then the average flow rate is only about 1 m/s (2.2 mph), which would imply the pressure difference of only about 500 Pa between the well and sea floor. Any person with a stout piece of plywood could actually block that off. The problem is that the weight of the sea floor will continue forcing more oil and gas into the well space even after you block the opening, so pressure will buildup and unless your obstruction is very sturdy the well will blowout again. Dragons flight (talk) 00:08, 22 May 2010 (UTC)

Why can't they just use a wider (4 -5 ft) pipe from the source to the surface and that would no doubt solve the problem of slushing up the pipe with frozen methane? —Preceding unsigned comment added by 98.221.254.154 (talk) 02:05, 22 May 2010 (UTC)

Actually the pipe would still slush up, it would just take longer. 67.170.215.166 (talk) 05:21, 22 May 2010 (UTC)

I would like to clear up a scientific inaccuracy that seems to be floating around in the above posts. The reservoir pressure is not exactly caused by the weight of the 18,000 feet of rock overhead. Rock is not a fluid (not a good one, at least); it does not behave like a hydraulic head; although the weight of the rock does contribute to the pressure, the real defining equations for pore pressure are a lot more complicated. The pore pressure contributes to, but must be converted into, an effective reservoir pressure. Finally, this can be used to estimate a pressure at the wellhead on the seafloor. The Terzaghi equation, in conjunction with reservoir characterization and geomechanical measurements, can be used to calculate the reservoir pore pressure; or an empirical law relating pore pressure to some other geomechanical property or observable from a borehole logging measurement. Finally, the fluid seep into the borehole needs to be modeled and eventually a hydraulic head can be calculated to determine the pressure at the exit point of the wellhead (on the seafloor) or at the ocean surface. To do all this, you need to know a lot of details about the fluid composition in the bore (probably drilling mud and other debris at this point), as well as details about the reservoir that only a privileged member of the BP E&P team would have access to. I just want to make sure nobody is thinking of applying the old "P = ρ g h" static pressure-head equation with the density of rock in a feeble effort to calculate the fluid pressure - it is unfortunately much more complicated than that. The short answer is, we don't know what pressure the oil is under as it rises to the well-head - the fact that there was a blowout indicates that neither did BP or its subcontractors. Nimur (talk) 02:44, 22 May 2010 (UTC)

We do know that at the time when it started to flow that the pressure in the reservoir was somewhere between the hydrostatic pressure (the pressure at the base of a column of water equal to the depth) and the lithostatic pressure (the pressure at the base of a column of rock equal to the depth). Most reservoirs are 'normally pressured' and lie close to the hydrostatic pressure, taking into account the column height of the hydrocarbons involved. Some reservoirs are 'overpressured' and lie closer to the lithostatic gradient but never reach it because high pressures will cause fracturing of the top seal (the impermeable layer that helps form the top of the 'trap') and this is known as the fracture gradient, so again we know that it will be less than that. After flow has started the pressure will start to reduce, something known as depletion, but the amount of depletion depends on the extent to which water flows into the reservoir as the hydrocarbon is removed, something known as 'aquifer support'. As to the blowout, the gas may have come from a shallower formation (unless this is associated gas i.e. coming out of solution from the oil), which should have been held back by the cement liner or casing in the wellbore above the reservoir. Mikenorton (talk) 13:12, 22 May 2010 (UTC)

I don't udnerstand why they can't just bring another rig to that location, send a pipe down and resume normal operations. Why not?--92.251.177.211 (talk) 20:30, 22 May 2010 (UTC)

BP are currently drilling two 'relief wells' to try and intersect the original wellbore, but it takes time and the target is rather small. Mikenorton (talk) 20:36, 22 May 2010 (UTC)

Field Strength of LHC Magnets

I am told that the magnets at the 27 km circumference LHC operate at 8.3 Teslas, while the protons contained in the beam have an energy of ~7 TeV (see Wikipedia LHC article). Trying to match these data up using simple physics fails, and so I'd like to know where my mistake(s) is/are.

As protons are travelling at near the speed of light:

$mv\approx {\frac {E}{c}}$

$F={\frac {mv^{2}}{r}}=Bqv\implies B={\frac {mv}{rq}}\approx {\frac {E}{crq}}$

Substituting in values:

$B={\frac {7\times 10^{12}{\mbox{ eV}}\times 1.602\times 10^{-19}{\mbox{ J eV}}^{-1}}{3\times 10^{8}{\mbox{ m s}}^{-1}\times 4300{\mbox{ m}}\times 1.602\times 10^{-19}{\mbox{ C}}}}=5.4{\mbox{ T}}$

I presume I've missed off some relativistic effects, but even when I tried to account for some of them, I still got around 5.4 Tesla. Any suggestions? --80.229.152.246 (talk) 15:46, 21 May 2010 (UTC)

(altered/corrected your ref tags - no reference section at bottom of this page)

Is it possible that the figures you've used are maximum operational limits - eg the magnets can go up to 8.3T safely ? (but are operated at a lower figure?)77.86.115.45 (talk) 16:19, 21 May 2010 (UTC)

there doesn't seem to be a reference for the 8.3T figure to get its context from.77.86.115.45 (talk) 16:23, 21 May 2010 (UTC)

There are a few mentions of 8.3 T being the required field in LHC: The Guide. --80.229.152.246 (talk) 17:38, 21 May 2010 (UTC)

Mmmh actually - plan B - the magnets aren't actually completely circular are they?? ie it's magnet/straight/magnet/straight etc? Thus the turning circle at the magnetic turning sections must be smaller than the radius of the machine - hence a higher magnetic field required - ie the colider shape in not a circle but a n-agon (polygon) (with rounded corners) - surely this must be the case? So radius is less than 4300m. 77.86.62.107 (talk) 18:31, 21 May 2010 (UTC)

I'm pretty sure it's quite circular. But what about length contraction? The magnet slightly ahead of the current position of the proton is length contracted toward the proton, so the radius might be lower than what you calculate. But it's not totally ahead of the proton, just slightly, so the contraction is only a fraction of the total speed. Ariel. (talk) 20:16, 21 May 2010 (UTC)

Fairly certain polygonal eg [13] states 1232 15m dipole magnets - so that's 18.5 km of bending magnets - but the circumference is 27km. 77.86.62.107 (talk) 20:27, 21 May 2010 (UTC)

(ec) That's correct. The bending magnets occupy only a portion of the ring's total circumference. The remainder contains quadrupole focusing magnets, experiments, and gaps between magnets. In total, the LHC contains 1232 dipole bending magnets, each with a length of approximately 15 meters. (That PDF link contains a number of other important specs for the bending magnets, as well.) 15 meters times 1200 magnets accounts for just 18 kilometers (about two thirds) of the total tunnel length. TenOfAllTrades(talk) 20:33, 21 May 2010 (UTC)

...back of envelope attempt at getting radius of curvature of magnetic sections - since for each turn (2pi/1232 radians) angle is small I assume sin x=x and cos x=1

r_effective=4300m , L=(27000m-18500m)/1232 (length of each straight section), A = 2pi/1232 (angle radians)

r=radius of curvature of magnetic sections

I get r_effective/r = (rA+L)/rA using similarity of triangles (approx since cosA~1)

solving for r (using pi=22/7)

gives r=4300x(15/22)

Thus using the original equation with the new r I get magnetic field = 5.4 x (22/15) = 7.92 (pretty close to the 8.3 quoted)

Looks like this method is probably along the right lines.?77.86.62.107 (talk) 21:36, 21 May 2010 (UTC)

I should probably point you back to the PDF that I linked in my response — it actually has more precise values for the length of each magnet, as well as explicitly specified bending radius and angle per magnet. The real magnet length is actually a bit less than 15 m — the specs say 14.3 m — which probably just about accounts for the discrepancy between your calculated field value and the nominal. TenOfAllTrades(talk) 03:11, 22 May 2010 (UTC)

doh, silly me I should stop skimreading - yep my estimate came out at ~2930m - the pdf gives ~2800m .. giving an unsuprising 8.3T for the required field which is spot on.77.86.62.107 (talk) 03:23, 22 May 2010 (UTC)

Thanks everyone. I'm glad to see it's not down to awkward relativistic effects like length contraction and the like (I did consider that but didn't think it'd have a large enough effect, plus I have no idea how to work that out...). --80.229.152.246 (talk) 15:45, 22 May 2010 (UTC)

Iron in high oxidation state

Is there any way to create iron compounds with an oxidation state of more than +3 using household chemicals? --Chemicalinterest (talk) 20:57, 21 May 2010 (UTC)

Potassium ferrate - you would probably only have access to the sodium compounds - sodium ferrate is more unstable (see http://library.sciencemadness.org/library/ferrates.html)

In sweden you can produce it from bleach possibly http://sv.wikipedia.org/wiki/Natriumferrat ?? seems to be confirmed by youtube http://www.youtube.com/watch?v=pUvdETUQPuo (I think this is probably true) 77.86.62.107 (talk) 21:49, 21 May 2010 (UTC)

I tried adding KOH and household bleach (NaClO) to ferric oxide but it didn't react. (Oh and I boiled it).--Chemicalinterest (talk) 22:42, 21 May 2010 (UTC)

Watch the youtube video linked above - you need strong bleach, and they boiled it.77.86.62.107 (talk) 22:47, 21 May 2010 (UTC)

Oh.. and the step were they add ammonia at the end - don't try that if there is excess bleach ammonia can react with it to make hydrazine - explosions can potentially follow... alternatively the reaction produces chloramines - which are toxic.. (or nitrogen trichloride even which too is explosive) In fact I wouldn't try this at home - boiling bleach sounds like a recipy for disaster in one form or another..77.86.62.107 (talk) 22:56, 21 May 2010 (UTC)

Pushing or pulling Asteroids

Lets say we have a spaceship that's powerful enough to move asteroids. Is it easier for it to push it or to pull it? ScienceApe (talk) 21:04, 21 May 2010 (UTC)

A joule is a joule is a joule. Presently, I don't believe we even have any technology that is capable of such a feat, so it's a purely speculative issue at this point, yes? Vranak (talk) 21:07, 21 May 2010 (UTC)

It would be easier to pull using the gravity inherent in the ship's mass, because that would not use any external energy. dude❶❽❶❽ (talk) 21:11, 21 May 2010 (UTC)

You still have to use energy to keep the gravity tractor in the right place. --Tango (talk) 21:13, 21 May 2010 (UTC)

Pushing is easier. Dauto (talk) 21:17, 21 May 2010 (UTC)

From an energy point of view it's the same, but from an engineering point of view pushing is easier. For two reasons: One you can just push the asteroid, and don't need some method of attaching to it. Two: If you pull, your exhaust gases will impact on the asteroid, which will push it back - you'd need some way to reroute your exhaust around the asteroid. Ariel. (talk) 21:42, 21 May 2010 (UTC)

Ok. But think of failure. If your're gunning it full steam towards an asteroid and the 'link', whatever that may be, fails, then you're going to crash into it (unless your distance is great, or you have good retro rockets, etc). If you're pulling it, you just go in the opposite direction. Vranak (talk) 21:44, 21 May 2010 (UTC)

That assumes pushing from a distance. If the asteroid is strong enough to be pushed from a single point without breaking up, the spacecraft can be brought right up against it first (in effect a soft landing) and then start pushing. However, you would need to keep the pushing force accurately aligned with the center of mass. --Anonymous, 23:08 UTC, May 21, 2010.

Exactly. In any case, a worst-case scenario looks a lot worse when you are pointing towards the 'roid, rather than away from it. Well, if it were remotely-operated, I suppose a hull breach isn't necessarily curtains. Vranak (talk) 00:16, 22 May 2010 (UTC)

I too would pull - for using you need a structure to transmit the pushing force from the front of the spaceship - but the force propelling the spaceship is probably at the back - would need a strengthened airframe - you also can't see where you are going..

For pulling all you need is some ropes - these can be attached close to the propulsion source - ropes can be long - gas back draft shouldn't be a problem..77.86.62.107 (talk) 21:46, 21 May 2010 (UTC)

Gas back draft most certainly is a problem. Or earth if you go far away the air disperses the gas. Not so in a vacuum. The gas will go directly toward the asteroid, and will totally cancel out the effect of the propulsion. It would be like trying to move a sailboat by attaching a fan to the boat and blowing on the sail. Ariel. (talk) 23:43, 21 May 2010 (UTC)

That depends on whether the gas molecules collide after being ejected - if so the gas will disperse (in a 'cone' shape) - I think it would be hard to make a rocket nozzle that outputs molecules that do not collide with one another - would require low gas densities - though it would be the most efficient.77.86.62.107 (talk) 00:34, 22 May 2010 (UTC)

For pushing you have to locate and get exactly behind the asteroid's center of mass or the thing will start spinning instead of going the direction you expect. For pulling this is not a problem. Cuddlyable3 (talk) 22:24, 21 May 2010 (UTC)

It's exactly the same problem for pulling. If the force, whatever the direction, doesn't go through the centre of mass then you will introduce a torque. If you are using a gravity tractor, then the force is automatically through the centre of mass, but if you are pulling it using a rigid scaffolding or something, then it could be a problem. If you are pulling it using a flexible cable, then the torque will be temporary and it will soon end up going through the centre of mass. You can avoid a torque when pushing by having the engine attached to the asteroid via a gimbal - that way you can make sure the thrust is straight "up", which means it goes through the centre of mass (actually, that may only be precisely true for a spherical asteroid, but I think the principle can be generalised). --Tango (talk) 22:39, 21 May 2010 (UTC)

Also for turning - if the spaceship has weak turning thrusters and powerful main engine fixed on axis then it is easier to pull since "thrust vectoring" can be used - whereas when pushing the turning thrusters would be required to turn the entire combined mass - depends on what sort of spaceship you're using I suppose...77.86.62.107 (talk) —Preceding undated comment added 22:34, 21 May 2010 (UTC).

see: Pendulum rocket fallacy.—eric 23:10, 21 May 2010 (UTC)

I don't think that fallacy is relevant. The IP is correct - if you are pulling the asteroid using a cable then all you need to do to turn is change the attitude of the rocket. If you are fixed to the asteroid, thrusting in a fixed direction and pushing it along then you would need to turn the whole asteroid. However, if you are fixed to the asteroid but can change the thrust direction of the main engine then you can use the main engine to turn the asteroid and it becomes pretty easy (in fact, it's probably just as easy as in the pulling case, since in both cases you will use the main engine to turn the asteroid). An alternative would be to push the asteroid using a rocket than can move around on the surface (probably hopping around - there is so little gravity on a typical asteroid that the thrust required to hop would be minimal, you could probably do it with an air horn!). --Tango (talk) 23:25, 21 May 2010 (UTC)

(I was assuming that someone would be steering the ship . but it is an interesting link)77.86.62.107 (talk) 00:37, 22 May 2010 (UTC)

I like the idea of pushing with a clamp-on linear accelerator, which mines the asteroid, ionizes it, and accelerates a small portion of it to near the speed of light as a source of propulsion, all powered by nuclear reactors, or better yet, a matter-antimatter reactor. StuRat (talk) 04:15, 22 May 2010 (UTC)

If you test that device at home, you'll need a user manual. Cuddlyable3 (talk) 22:42, 22 May 2010 (UTC)

Car Mechanics...... power steering

Hi evry one ... my car power steering system breaks down .... so i tried to find out how it works , i googled it , to find this ... that the system use a pump attached to the engine (use engine power to compress hydrulic oil) in the system to maximize your hand power and make it easier to rotate the car .... so while searching i found that the oil pump compress the system faster at higher rpms (revolve per minute) .... which leads to more sensitive steering at higher speeds ... should'nt it be the other way around ...? as a safty measure the steering should have a slower response at higher speeds ...? --Mjaafreh2008 (talk) 21:47, 21 May 2010 (UTC)

Did you read in the article Power steering this: "...at high engine speeds the steering would naturally operate faster than at low engine speeds. Because this would be undesirable, a restricting orifice and flow control valve are used to direct some of the pump's output back to the hydraulic reservoir at high engine speeds." ? Cuddlyable3 (talk) 22:19, 21 May 2010 (UTC)

I don't know that it's done intentionally, higher oil pressure is a necessary side-effect of more RPMs (ergo more mechanical and thermal stress). I don't think increasing oil pressure would increase steering sensitivity, but I do think it would increase the power that goes into turning the wheels, which is better used at high speeds than at low speeds - as speed increases, so does momentum, which means changing the direction of the car requires a heck of a lot more force. I can safely drive at 20mph to the corner market lot with no power steering at all, I just have to put some muscle into turning it. But I don't want to imagine what happens if I drove unpowered at 75mph on the highway; I've done it, but at great risk - if something happened at that speed (blowout, shenanigans with other cars, etc) a gorilla couldn't control that wheel, let alone me. ZigSaw 12:14, 24 May 2010 (UTC)

May 22

If Earth was great big ball of magnetism

If the earth was magically replaced with a new earth made totally from a strong magnetic material like neodymium what sort of impact would that have on the solar system? I know that gravity is really weak compared to the other forces so i'm just curious would an earth of neodymium pull other planets towards it? Would it have any effect on the sun? Mike --87.112.183.70 (talk) 01:17, 22 May 2010 (UTC)

I don't think so -- at the sorts of interplanetary distances involved, the gravitational force would still be much more of a factor than the magnetic force. Keep in mind, too, that the other planets would still be non-magnetic. FWiW 67.170.215.166 (talk) 05:17, 22 May 2010 (UTC)

This is a terrific question that I know will have several people puzzling. I can't speak much to the change in Earth's natural magnetic field at all - I will defer to someone who knows more about it - and I'm not sure how the polarity is set up in those Nd magnets. That said, most planets have natural magnetic fields, and if the field lines from two bodies reinforce each other, they will attract according to the cube of the distance from each other. This tapers off much more quickly than gravity, but even if it didn't, Earth's field may be strong but even Jupiter's, the strongest in the solar system, is relatively weak and will likely not result in much orbital disturbance.

It takes two good fields to magnetically tango. When magnets pick up pieces of metal like paperclips they do it by inducing a temporary field in the paperclip, because the iron in a paperclip is something that can quickly align as a magnet and then fall back out of it, depending on what other fields are in the environment (so it can attract itself to either pole of a magnet by rearranging itself, for example). A planet is not made out of this "ferromagnetic material". Most of them have heavy cores of iron or nickel, but those are far too high temperature to hold an attractive arrangement together to attract itself to the Nd Earth. However, Nd magnets are strong enough to induce magnetic fields in even non-ferromagnetic materials, even humans, and thus can make for neat household tricks (try dropping one down an iron tube).

In conclusion, I don't think this giant Nd Earth will have much direct effect on other planets, though someone will probably prove me wrong. SamuelRiv (talk) 05:24, 22 May 2010 (UTC)

I think that the neat trick you're thinking of involves dropping a strong magnet down a copper tube. The magnet will simply stick to an iron tube. APL (talk) 07:42, 22 May 2010 (UTC)

Now you've got me curious. What happens? Vimescarrot (talk) 07:57, 22 May 2010 (UTC)

assuming you've not already google'd it - here's a youtube video of what happens. (http://www.youtube.com/watch?v=30oPZO_z7-4) ny156uk (talk) 09:13, 22 May 2010 (UTC)

Nifty! Vimescarrot (talk) 15:27, 22 May 2010 (UTC)

This super magnetic earth will have an impact on solar wind it will probably drag all the solar wind nearby and accelerate it to the magnetic pole. It might also attract iron asteroids - especially if given enough time. I think the first order of business is calculating just how strong the magnet would be. Ariel. (talk) 02:11, 23 May 2010 (UTC)

rust forceps

i bough some German stainless steel Surgical OCHSNER Forceps. i put them on my sink counter. a few weeks later a small amount of rust appeared. hows that possible. —Preceding unsigned comment added by Tom12350 (talk • contribs) 04:57, 22 May 2010 (UTC)

What's your sink counter made of? If could the rust have come from that and not the forceps? This used as a source in stainless steel only says that stainless steel rusts less easily than normal steel. I'm no chemist though, hopefully someone can explain in more detail. 131.111.30.21 (talk) 08:59, 22 May 2010 (UTC)

Stainless steel is very resistant to oxidation by oxygen gas, where it forms a thin protective layer of chromium(III) oxide. If there is acid, the coating dissolves, starting the corrosion (although the rust dissolves too). If there is strong alkali, the coating dissolves, and some rust forms which is insoluble in alkali (iron is not amphoteric). But you shouldn't have strong acids and alkalis on your sink. --Chemicalinterest (talk) 10:51, 22 May 2010 (UTC)

[14] [15] Rust spots on stainless steel happen, for a variety of reasons.77.86.62.107 (talk) 14:51, 22 May 2010 (UTC)

Weather recce

What's an aerometeorograph, and what atmospheric parameters does it measure? 67.170.215.166 (talk) 06:06, 22 May 2010 (UTC)

From here "A self-recording instrument used on aircraft for the simultaneous recording of atmospheric pressure, temperature, and humidity." APL (talk) 07:30, 22 May 2010 (UTC)

Cool, three essential parameters measured with one instrument! Now, does anyone happen to know its typical weight and size, and also whether it's a self-contained instrument or whether it has to be hooked up to the plane's static port or OAT gauge? Thanks for the info! 67.170.215.166 (talk) 02:53, 23 May 2010 (UTC)

Update: Just looked up some pictures of modern units, they're quite small (about the size of your typical battery-powered portable emergency radio). So no problem about the size; the only thing I need to know is, is it self-contained or does it hook up to the plane's instrument systems? 67.170.215.166 (talk) 07:17, 23 May 2010 (UTC)

Can the acoustic guitar hurt your hearing?

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the talk page discussion (if a link has been provided). --TenOfAllTrades(talk) 13:40, 22 May 2010 (UTC)

TenOfAllTrades(talk) 13:40, 22 May 2010 (UTC)

Too fast to be an Iridium flare... so what was it?

I sat beneath the stars tonight for about an hour. I no longer have a grasp of the night sky, so all I can say is I was facing southwest (the Big Dipper was behind me somewhat). At one point, I saw what looked like a camera flash go off, but it was a pinpoint of light. It was extremely quick, no "few seconds" or "trail" that the Satellite flare article talked about. Then I noticed something peculiar... I kept staring at that spot and there was a second, almost imperceptible flash, just a hair to the left of the original flash. Huh! Anyway, time goes on and I'm staring to the northwest, closer to the Big Dipper, and again, there is a microburst of light way up in the heavens. This time I stared and stared, hoping to corroborate the secondary flash, and sure enough, after a few seconds, and just a fraction of some unknown stellar distance from the original flash was a second "pop" of light... What's up there, and is it rotating? I've seen dozens of "normal" satellites that are a constant reflection, a dot moving slowly across the night sky. I've never seen this before in my life. Any ideas? SR-71 taking pictures of me? :D – Kerαunoςcopia^◁_galaxies 09:17, 22 May 2010 (UTC)

It might be an airplane doing combat manuevers in the air. It also could be a meteor. Firecrackers? --Chemicalinterest (talk) 11:06, 22 May 2010 (UTC)

Without having seen it, it's hard to say for certain. It's also worth remembering that one's eyes can play tricks under low-light conditions. (For example, the second 'flash' might be just some sort of afterimage that you're seeing just because you're looking very hard for it. As well, to dark-adjusted eyes an object doesn't have to be particularly bright for it to look quite bright.) A couple of guesses: a meteor following a trail aimed almost directly at you, so that it didn't appear to move appreciably as it rapidly brightened and then disappeared. If the rock happened to break into more than one fragment, you might see a second flash. Another explanation could be tumbling space debris — the solar panels on a retired or 'lost' satellite, etc. That reflection would tend to have a much faster 'rise time' than an Iridium flare, and you might get a second flash as the satellite tumbled around. TenOfAllTrades(talk) 13:12, 22 May 2010 (UTC)

A fundamental problem we have here is not knowing how high was the artefact that caused the brief flashes. It could indeed be something as simple as a plane at altitude and you caught a solar reflection, you don't say how long after sunset this occurred. However the fact that it happened again in a different part of the sky makes me believe that it was some sort of image created by your eye or optic system. There are several non-pathological causes for the effect of "seeing stars" in a medical sense and I am not inferring that you have a medical condition that requires attention, I suggest this may be a possible reason for seeing microflashes of light. Richard Avery (talk) 14:59, 22 May 2010 (UTC)

It could easily be a satellite flare, just not an iridium reflection. There are other objects tumbling rapidly that could give a flash. If it is short you wont see a trail. Graeme Bartlett (talk) 22:09, 22 May 2010 (UTC)

Could it be a plane's anti-collision strobe lights? Many civilian planes have them, and they make bright white flashes every couple seconds. And if the plane was at high altitude (like an airliner at 30000 feet), then you can see the flashes but not hear the engine noise. FWiW 67.170.215.166 (talk) 02:58, 23 May 2010 (UTC)

If you remember the exact time, check the Heavens-above website. Count Iblis (talk) 16:56, 23 May 2010 (UTC)

Thanks, all. It wasn't an eye problem, it couldn't have been an airplane because I was watching for that, and beside, the night was absolutely crystal clear pitch black loaded with stars, and nothing was moving up there, and thanks for the Heavens Above website, but unfortunately I have no clue what time it was. Anywhere between 4 and 5 in the morning, but i have no watch. – Kerαunoςcopia^◁_galaxies 19:20, 23 May 2010 (UTC)

How many carbon black add in polypropelene polymers from protection SUN LIGHT

Dear, Plese, find answer headline and give me reply. thanks, Mr. jatin —Preceding unsigned comment added by Mjhirpara (talk • contribs) 12:14, 22 May 2010 (UTC)

More carbon black produces increased uv resistance.

This product [16] uses 3% carbon black.77.86.62.107 (talk) 15:03, 22 May 2010 (UTC)

See this book [17]77.86.62.107 (talk) 15:06, 22 May 2010 (UTC)

Iodine oxidation

Is sodium hypochlorite strong enough to oxidize elemental iodine (in its dilute state as household bleach)? --Chemicalinterest (talk) 12:19, 22 May 2010 (UTC)

Look up the reduction potentials for Cl⁺¹ → Cl⁰ or Cl^–1 compared to I⁰ → I⁺¹ to see which is stronger/able to oxidize or reduce which when you have these two redox half-reactions balanced. DMacks (talk) 15:06, 22 May 2010 (UTC)

There's a number of issues with this reaction:

• hypochlorite solutions are strongly basic - so the standard electrode potentials will need converting, or may not be applicable
  • particularily : Iodine disproportionates in alkaline solution to iodide and iodate
• Additionally Iodine reacts with chloride to form I₂Cl- and other reactions.

There's some more detail on iodine redox here [18] 77.86.62.107 , the chlorine potentials are also in this book a few pages before. (talk) 15:24, 22 May 2010 (UTC)

I never find the reduction potential for OCl^- + H₂O + 2 e^- → Cl^- + 2 OH^-; only see it for reduction to Cl₂. The iodide probably will be oxidized by NaClO when it is formed. --Chemicalinterest (talk) 17:04, 22 May 2010 (UTC)

It's in the above link, page 74 section C E=0.890V (in basic solution - not at [H+] = 1mol/dm3)

Probably the reason why it's never found as a standard E is that ClO- is unstable under standard (ie acidic) electrode conditions.87.102.18.191 (talk) 17:11, 22 May 2010 (UTC)

FWIW, "put a drop of solution on starch/iodide paper" is a standard test my students use for presence of hypochlorite in solution; turns dark if there is oxidizer available. See starch indicator and iodine test for some backround on what this might mean chemically. DMacks (talk) 18:55, 22 May 2010 (UTC)

Wembley Stadium grass - too dark?

Are the problems with the Wembley Stadium pitch simply due to the fact that the design of the stadium (high walls, roof) means that the grass does not get enough sunlight to grow properly? 92.28.248.33 (talk) 13:06, 22 May 2010 (UTC)

It seems unlikely, grass doesn't require a particularly high level of photosynthetically active radiation to grow. In fact at my house, the grass grows longer in the shade since there is more water available due to less evaporation. I'm not familiar with stadiums but I can't believe that Wembley is particularly different to any others and you'd think that they would have thought about it during the design stage. Reading this it sounds like it is more of a problem with it not being laid long enough before a game is played for a strong mat of roots to grow and form a good surface. 131.111.30.21 (talk) 16:33, 22 May 2010 (UTC)

The roof of Wembley was specifically designed to maximise the sunlight on the pitch, for the grass - that's why it's retractable. Vimescarrot (talk) 17:46, 22 May 2010 (UTC)

The stadium is in London, which is on the same latitude as Newfoundland, so it would not get as much intensity of sunlight as similar designs of stadium would in most parts of the United States for example. The grass is also 4 metres lower than it used to be, and the old design was less raked and roofless as far as I recall. 92.15.9.117 (talk) 18:04, 22 May 2010 (UTC)

dimple above penis

I have noticed that some men have a slight dimple just above the spot where the penis meets the pubis (this is normally only apparent if the pubic hair is shaved). Is this a medically recognised anatomical feature, and if so, what is it's name? Little radiolarian (talk) 13:14, 22 May 2010 (UTC)

Do you mean Apollo's belt? --Jayron32 04:25, 23 May 2010 (UTC)

Jayron -- I think he refers to the dimple in the midsagittal plane. It's a space between muscles that doesn't provide the support for the skin in that region as seen in the immediately surrounding areas -- anatomically, the space will fall in the midsagittal plane and will correspond to the skin and fatty tissue superficial to the suspensory ligament of the penis, just inferior to the pubic symphysis. DRosenbach ^{(Talk | Contribs)} 04:30, 23 May 2010 (UTC)

That certainly sounds like the same spot I'm describing. Would it be correct to describe this dimple as a surface feature of the pubic symphysis? If not, how would you refer to it (on the rare occasions one might have reason to)? Little radiolarian (talk) 15:25, 23 May 2010 (UTC)

I dreamt about this question last night, graphic imagery and all. Didn't even remember until I was passing through this question. – Kerαunoςcopia^◁_galaxies 19:16, 23 May 2010 (UTC)

According to the anatomy text I'm using (Moore), the pubic symphysis is too inferior to palpate -- probably because of both a low position and the erectile tissue being too massive to poke through. DRosenbach ^{(Talk | Contribs)} 01:28, 24 May 2010 (UTC)

The origin of life!!!!!!

I want to know how it was successfully verified that life on earth has arisen from complex molecules such as methane and oxygen was not present during the initial formation of life on earth? —Preceding unsigned comment added by Hitarth21 (talk • contribs) 14:58, 22 May 2010 (UTC)

Hi, your sentence is very confusing, can you rewrite it? Thanks. Beach drifter (talk) 15:00, 22 May 2010 (UTC)

Our knowledge and understanding of abiogenesis is very limited. There are some educated guesses about how it might have happened (see that article for details), but we don't really know. --Tango (talk) 15:50, 22 May 2010 (UTC)

TWO SCIENTIST DID AN EXPERIMENT: they took a round bottom flask, put two electrodes in it,filled it half with water, and put some rare gasses in same proportion they thought would have been present at the time of origin. they kept this setup for weeks at 100degree Celsius. electrodes are used for sparking mimicking lightning. and after weeks lo and behold1 TYHEY found key compounds needed to let life exist. THIS EXPERIMENT WAS CALLED MILLER'S EXPERIMENT ON THE NAME OF ONE OF THE GEEK. GOOGLE IT --Myownid420 (talk) 15:53, 22 May 2010 (UTC)

You're thinking of the Miller-Urey experiment. It was an important step in thinking about how life came about, though people today realize that the actual composition that they used probably wasn't very representative of Earth's early atmosphere. However, similar experiments have been done using other compositions, sometimes with interesting results. Buddy431 (talk) 16:23, 22 May 2010 (UTC)

Here are some of the problems with your original post:

1) Methane and oxygen aren't complex molecules, they are simple molecules (CH₄ and O₂). Oxygen, of course, is also a chemical element, O, but isn't normally found as a single atom.

2) The "complex molecules" you were probably thinking of are amino acids, the building blocks of proteins.

3) Then when you ask about whether scientists "verified that life on earth has arisen" from this process, you must realize that scientist can only propose a hypothesis that this is how it happened, as there's no fossil record of the original life forms. StuRat (talk) 16:30, 22 May 2010 (UTC)

The initial stages of the origin of life are still not clearly understood. To me it seems most likely that deep ocean vents are where the action took place. Regardless of that, there is very strong evidence that significant oxygen levels didn't show up until about a billion years ago -- the rocks that formed at the surface prior to that are not oxidized as they would be if high levels of oxygen had been present. Looie496 (talk) 16:52, 22 May 2010 (UTC)

AFAIK it is considered that oxygen was likely poisonous to early life. Vespine (talk) 22:55, 23 May 2010 (UTC)

Germ cell tumor

Whats the prognosis of a metastatic germ cell tumor —Preceding unsigned comment added by 24.97.164.250 (talk) 15:13, 22 May 2010 (UTC)

I assume you've read "Germ cell tumor#Prognosis"? Remember that Wikipedia does not give medical advice (see WP:MEDICAL). Gabbe (talk) 17:10, 22 May 2010 (UTC)

planets coming in align

in how many years does all planets come in one line. is it even possible or not? When they will align, will not it anyhow efffect Earth's life? if so then how.

<IN MY CLASS TEST ONCE I MADE ALL THE PLANETS IN ONE LINE AND MY TEACHER ASKED ME "WHAT IS THE PROBABILITY OF THIS". I SAID "MAY NOT IN COMING THOUSANDS OF LIGHT YEARS BUT SOME DAY IT WILL HAPPEN". I WANNA KNOW I WAS CORRECT OR NOT>

See Syzygy. How often it happens depends on how precisely you want them to line up. If you're happy with them just being in the same quadrant (ie. a 90 degree wide sector) then it will happen far more often than if you require them to be within a 1 degree sector, say. As for what effect it would have - none at all. About 70% of the combined mass of the planets is Jupiter, so all the planets acting together couldn't do anything significantly more than Jupiter can do on its own, which isn't much (as far as the Earth is concerned). --Tango (talk) 15:57, 22 May 2010 (UTC)

And when you consider the relative gravitational influence of solar system bodies on the Earth, you stop caring after the moon and the sun. Jupiter isn't even the most influential planet (it's 1/10th the effect of Venus), but none of them are meaningfully relevant. — Lomn 19:44, 22 May 2010 (UTC)

Ah, yes, I forgot it's tidal forces, not direct gravitational forces, that matter, so we need the cube of distance not the square. I believe Jupiter has the largest gravitational force out of the planets on Earth, just not the largest tidal force. Thanks for the link! --Tango (talk) 21:25, 22 May 2010 (UTC)

And a light-year is a unit of length, not of time. --Магьосник (talk) 16:37, 22 May 2010 (UTC)

Isn't there a particular name for this phenomenon?--Myownid420 (talk) 02:18, 23 May 2010 (UTC)

If you count Pluto as a planet, Neptune and Pluto "align" every 492 years ("align" = conjoin in geocentric celestial longitude -- it would be better to be heliocentric, but this is just for illustration). Uranus and Pluto align every 115 and 165 years, alternating. Uranus and Neptune align every 171 years. Saturn and Uranus align every 45 years. Saturn and Pluto align every 30-plus years, as do Saturn and Neptune. Jupiter and Saturn align every 29 years. And so on. Given that the solar system has been and will be around for billions of years, it's likely that at some point all nine planets will be within one degree of each other in heliocentric "longitude" because the product of all the periods is probably much less than several billion years. However, if you want alignment to within one arc-second, it seems unliekly that even the products of the periods will realistically indicate an exact nine-planet alignment, though I don't know the math for this. Anyone else? 63.17.50.130 (talk) 02:43, 23 May 2010 (UTC)

This data is based on short term observations. The solar system is basically an n-body problem; in the short term it can be predictable, but in the long term it becomes highly chaotic. So, we can pretty easily predict how often two bodies will be in line with the sun; but once we start waiting for three and four and five bodies to align in such a way, the time frame becomes long enough between occurances that chaotic effects take over and it literally becomes impossible to predict. --Jayron32 04:22, 23 May 2010 (UTC)

This happened about 5 years ago, all the red top papers in the UK were predicting workd disaster...nothing happened, just a normal day at the office. therefore, it does happen, rarely, but is of no significance to anyone.

Solid phase extraction and Chromatography

Hi, I have just read both Solid phase extraction and Chromatography pages but I haven’t found the difference between techniques. I mean, they do the same thing and exploit the same principle or not? Thanks so much in advance, I ‘m studying Forensic pathology for next month exam.--151.53.91.218 (talk) 16:51, 22 May 2010 (UTC)

SPE deals with making the desired analyte specifically soluble/extracted or insoluble/stuck-to-solid-phase, the other starts and ends with the desired analyte in solution merely passed through. The key to SPE is where that article states "either the desired analytes of interest or undesired impurities in the sample are retained on the stationary phase" (emphasis mine) as opposed to the more general idea of chromatography "passing a mixture [...] through a stationary phase, [...] Subtle differences in a compound's partition coefficient result in differential retention on the stationary phase". Differential retention causes elution time to vary vs "retained or not-retained". DMacks (talk) 18:50, 22 May 2010 (UTC)

updates based on scientific fact

Shrimp are bottom feeders meaning their diet may include toxic substances including radioactive particles. However, since 1970 shrimp have been farmed in non-toxic environments. Consequently do any of the religions which in the past have excluded them from the diet now permit such non-toxic shrimp to be labeled "Kosher"? 71.100.3.228 (talk) 19:53, 22 May 2010 (UTC)

Toxins possibly being present in food has nothing to do with the food being or not being Kosher. Beach drifter (talk) 20:00, 22 May 2010 (UTC)

I think the toxin example is a bad one because it presumes to know the intent of the law, which would not sit with a religious person terribly well. (It assumes they have secular goals behind them; that is how an outsider views such things, not an insider.) But there are modern updates to things like kosher laws—for example, there is an entire industry of appliances designed to conform with Sabbath strictures as they are interpreted to apply to modern technology. See: Sabbath mode. In Judaism, there are rabbis who get together and debate whether or not, say, flicking a switch violates the strictures against "work", or whether setting an oven to heat up violates strictures against lighting a fire, and so on. --Mr.98 (talk) 20:52, 22 May 2010 (UTC)

To elaborate on Mr.98's concise post above, the laws of Judaism are immutable and the biblical violation of eating seafood that does not possess both fins and (easily scrape-off-able) scales (Leviticus 11:9) does not hinge on the toxicity or other physical uncleanliness of these organisms. DRosenbach ^{(Talk | Contribs)} 04:37, 23 May 2010 (UTC)

Okay then I'm really stumped here trying to explain why in this modern day why such ancient rules are not arbitrary but rather mandatory, unless they are intended to be arbitrary so they can serve more as test of obedience rather than anything else. If that is THE CASE and its just a matter of proving loyalty through compliance rather than compliance serving a practical purpose then not updating such laws makes more sense. 71.100.3.228 (talk) 07:54, 23 May 2010 (UTC)

"Why a religion has a certain rule" is not a scientific question. DMacks (talk) 08:13, 23 May 2010 (UTC)

Then what in your opinion is the purpose for a religion having rules? 71.100.3.228 (talk) 20:04, 23 May 2010 (UTC)

In any case, much of Judaism in particular is about doing what the law says even though you don't understand it. It is not and does not claim to be scientific. If you'd like a humorous send-up of Orthodox Jewish thought, which nonetheless gives a great (and entertaining) primer as to the logic behind it, I highly recommend Shalom Auslander's hilarious Foreskin's Lament: A Memoir. The basic philosophy is that you do what God says because God says to do it. As for whether the origin of the laws are based in some kind of secular purpose, well, there's been a lot of speculation about that, and that would be interesting for the anthropologist, but it would not be relevant to anyone practicing the religion. And I will note that my very reform cousins did not keep kosher at all, even at their bar mitzvahs and things like that (they served Hawaiian pizza, if you can believe it). There are multiple strains of thought within any religious heading. (I write all this as a nonreligious person myself, so if I offend anyone or have grossly caricatured a complicated thing, I apologize ahead of time.) --Mr.98 (talk) 12:53, 23 May 2010 (UTC)

What comes to mind are certain religious real world physical "journeys" in which the individual believer marks out the entire journey with a prone position to show devotion to its head. In any practical sense walking would be an update or flying in a plane but since the purpose is to show devotion to the religion's head by lying prone the entire length of the journey and walking or flying would not show this level of devotion they must be ruled out. From this perspective then I can see why religious rules would not be subject to update. 71.100.3.228 (talk) 20:12, 23 May 2010 (UTC)

Religious rules are subject to update - just, usually, not for scientific reason. Christianity is Judaism 2.0 (well, actually, a bag from 2.0 to 4.5 with plenty of mutually incompatible patches ;-) and Islam is essentially a merger of both rewritten from scratch. Looking at the early history of Christianity (which essentially started out as a jewish sect) shows significant debate of which laws apply to jewish Christians, and to gentile Christians. The laws given to Noah (don't kill, don't eat blood) were deemed to apply to all Christians (although the first has been very much rationalised away, and the second largely forgotten by now), but the Kashrut and circumcision were on the table for a while, too (with Paul being one of the strongest opponents of applying them to gentiles). --Stephan Schulz (talk) 20:46, 23 May 2010 (UTC)

Thanks for the Kashrut link. I have a friend who is developing meals that comply with individual diet plans which are based on varying amounts of commonly available foods which Kashrut will help guide. For instance, farmed shrimp was on the list until now. It would be nice in some cases though if the rules were updated to include farmed shrimp. 71.100.3.228 (talk) 20:59, 23 May 2010 (UTC)

(outdent) Religious observance is one of those things that really doesn't take kindly to an outsider trying to find technicalities or adjustments in how to apply or accommodate them. If you're trying to be polite and make certain populations feel welcome, you definitely take them on their own terms, however obsolete, confusing, nit-picky, or technicality/confusing-to-you they might seem. In fact, one of the tenets of Judaism and "follow its laws" I often hear is that you shouldn't try to find loopholes to excuse why you don't want to follow an observance (the flip side being whole movements that have taken a coherent look at deciding what observances are appropriate for modern-day). Or in a milder form, better to play it safe than to accidentally actually violate a law while trying to just tread close to the edge. Really, if you're trying to host an event where keeping kosher (to some level) matters (for some guests) ask them what they feel comfortable with. There's strictly kosher, who wouldn't even eat off your dishware and wouldn't drive to your venue on Saturday, there's "pretty kosher" who would be happy with a vegetarian option rather than putting you to the effort of cooking something really kosher, there's "kosher style" who would eat non-kosher beef but not a cheeseburger, etc. Just like there's vegan, lacto-ovo-vegetarian, "no red meat", etc. Actually, having a real vegetarian option (an actual entree, not just the side-salad) is a pretty good way to solve many different special diets (health, moral, religious). DMacks (talk) 21:45, 23 May 2010 (UTC)

magnetism versus temperature

what is the formula that relates and objects temperature to its magnetism? 71.100.3.228 (talk) 20:01, 22 May 2010 (UTC)

I'm not aware of one - maybe you were thinking of the Curie temperature .87.102.18.191 (talk) 20:25, 22 May 2010 (UTC)

So the state of magnetism undergoes a similar transition as state of matter phase change in which changes occur at junctures rather than continuously? 71.100.3.228 (talk) 20:49, 23 May 2010 (UTC)

Niel ?

I keep thinking I've heard of a "Niel temperature" - but search shows nothing. (Not Niels Bohr - I think it was a surname)

Is there a similarly name temperature or point - I'm sure it was a transition or phase change temperature.87.102.18.191 (talk) 20:27, 22 May 2010 (UTC)

Annealing temperature? --BozMo talk 20:34, 22 May 2010 (UTC)

:) (no) 87.102.18.191 (talk) 21:20, 22 May 2010 (UTC)

The Néel temperature is the temperature above which an antiferromagnetic material becomes paramagnetic. Cuddlyable3 (talk) 21:29, 22 May 2010 (UTC) Cuddlyable3 (talk) 21:29, 22 May 2010 (UTC)

Yes thanks. 87.102.18.191 (talk) 21:49, 22 May 2010 (UTC)

Resolved

What metals were thrown out by the icelandic volcano?

What heavy metals were ejected by the icelandic volcano?--92.251.177.211 (talk) 20:55, 22 May 2010 (UTC)

The material ejected by the volcano would have been basically basalt, which has metals in the form of silicates and oxides but none of the heavy metals are likely to be present other than in trace amounts, as far as I know. Mikenorton (talk) 21:26, 22 May 2010 (UTC)

Heavy metals are found in only trace amounts in basalt - but the overall effect of a volcanic eruption is to increase the levels of heavy metals in the surrounding area (in general) http://www.google.co.uk/search?hl=en&q=volcano+heavy+metal+emmision&meta=

In norway no effect had been noticed expected in this report http://www.niva.no/symfoni/infoportal/publikasjon.nsf/.vieEngInterForsideNIVA/1135331028BA9759C125770E00278CE0?OpenDocument&Category=&m1=News

[19] people are measuring this, but as far as I can tell the results aren't readily available as yet.87.102.18.191 (talk) 13:21, 23 May 2010 (UTC)

Is there any animal that can 'emit' fire?

Years and years ago I saw a wildlife documentary that featured a rainforest insect of some kind which (IIRC) as a defence mechanism was able to squirt a stream of *something* from its hindquarters which then spontaneously ignited in contact with the air, producing a small jet of flame. For some reason, I ended up discussing this with someone today, who insisted that I was wrong and asserted that there is no such and never has been any such creature. I'm open to the possibility that my memory is playing tricks on me and that I've mixed up something like a bombardier beetle (I looked that up first, thinking that it may have been what I was remembering) with Pokemon, or dragons - or that I saw it in a dream, or whatever.

So, does anyone know if there really is a bug, or anything else out there that can do this? --Kurt Shaped Box (talk) 21:05, 22 May 2010 (UTC)

I think you're just thinking of the bombardier beetle. There are no fire-breathing anything (other than people). --Mr.98 (talk) 22:07, 22 May 2010 (UTC)

Dragon —Preceding unsigned comment added by 79.76.233.61 (talk) 23:44, 22 May 2010 (UTC)

Animal, mythological creature. These are not equivalent, 79. Vranak (talk) 01:59, 23 May 2010 (UTC)

Salamanders are often associated with fire, though in reality they have very little to do with it. Buddy431 (talk) 04:12, 23 May 2010 (UTC)

It used to be thought that salamanders derive from fire, but it was later shown that they merely crawl from ground detritus when fire causes them to leave. See Slifkin's Mysterious Creatures (Targum Press 2003) ISBN 1-56871-248-0 (republished as Sacred Monsters) for a thorough review. DRosenbach ^{(Talk | Contribs)} 04:40, 23 May 2010 (UTC)

Any creature capable of setting fire to its environment would have made itself extinct by now.--Shantavira|^{feed me} 06:16, 23 May 2010 (UTC)

The conclusion being, any animal capable of emitting fire would have to live in a difficult-to-ignite environment. Vimescarrot (talk) 08:54, 23 May 2010 (UTC)

Or just be careful about what they ignite. I mean, humans are animals that are capable of setting fire to their environment. Yes, we've burnt ourselves a few times doing that, but it's hardly an evolutionary impossibility! --Mr.98 (talk) 18:49, 23 May 2010 (UTC)

Yes, but we've only been around for the blink of an eye. The (non-avian) dinosaurs still have about a factor of 1000 on us, and see where they are now. --Stephan Schulz (talk) 20:50, 23 May 2010 (UTC)

Not necessarily. Certain pines (I think Jack Pines are one), for example, need fire in order to germinate. If there isn't a periodic wildfire, they can be crowded out by other trees. (This has happened in portions of the western U.S., where there has been a "suppress all wildfires" policy for several decades.) Right now they require externally initiated fires, but one could easily imagine a hypothetical situation where a pine recognizes that it's being crowded by other species, so produces copious amounts of (fire-resistant) seeds, and then sets fire to the forest. Other species will be pushed out, and the seedlings now have ash-enriched soil to grow in. This might allow them to spread to wetter climates, where wildfires are not as wide ranging. -- 174.24.200.38 (talk) 17:48, 23 May 2010 (UTC)

A 2005 forum post [20] says: "There was an article a year or two ago in the NY Times, from a number of scientists who said that a fire-breathing animal was biologically possible." I haven't found the article. PrimeHunter (talk) 00:25, 24 May 2010 (UTC)

You're not thinking of fireflies, are you? (I wish I was a firefly I never would be glum Cos how could you be gloomy When the sun shines from your bum?)--TammyMoet (talk) 09:14, 23 May 2010 (UTC)

Black hole paradox

After watching an explanation of the black hole paradox from Leonard Susskind, the explanation made first at sense, but further thought has left me only more confused. First, a quick explanation of the paradox:

• When person 1 watching person 2 enter into a black hole, person 2 appears to freeze, and time for him stops due to the gravity. Person 2 will never progress beyond the event horizon from person 1's view.
• Time, however, does not stop for person 2; from his perspective, he will sail right past the event horizon.
• Point 1 appears to conflict with point 2. Thus anything done by person 2 inside of the horizon will be irretrievably lost to the outside world - this shouldn't happen though. Physics says that, in theory, person 1, with a perfect view of what's occurring, should be able to reconstruct person 2's past perfectly.
• The solution, as explain by Susskind and apparently mostly accepted by physicists, is that the information is stored on the surface of the event horizon, an unfathomably hot place where matter is squished into a two-dimensional (or essentially two-dimensional) plane.

What I don't understand is this:

1. For person 2, time on the outside world should go faster and faster. Right before reaching the event horizon, the world will speed up to infinite time. What then to make of what person 2 observes after passing the even horizon? (this situation, by the way, is far from just theoretical: the spaghettification on a smaller sized black hole apparently won't occur on supermassive black holes).
2. What of the matter towards the center of the collapsing star that becomes a black hole? That matter has no way of being "stuck" on the event horizon and as such wouldn't be visible as the event horizon slowly evaporates.
3. What happens to matter immediately inside the event horizon upon collapse? The gravity there would insist on a field faster than the speed of light. This seems to violate the laws of nature.

Magog the Ogre (talk) 21:25, 22 May 2010 (UTC)

I'm not sure what the problem is in your first question. Somebody falling into a black hole will see the outside world sped up (and massively distorted) and will observe things happening billions of years after they crossed the line in the few hours (at most) they can survive before being ripped apart, that's just the way it is. For your other questions, I don't think the problem exists since the collapse will happen from the inside out. The centre of the star will be the densest bit, so will become a black hole first and the rest of the star will fall into it. The event horizon will start out with very tiny diameter (you probably need a theory of quantum gravity to describe that bit) and grow. Your questions seems to be based on the assumption that the event horizon forms instantly at its final size, which isn't the case. --Tango (talk) 02:23, 23 May 2010 (UTC)

1. Remember that person 2 can only see what happens in his past light cone which will not include a infinite amount of the time of person 1
2. Tango answered question 2 pretty well above.
3. I'm not sure I understand your question, but be asured that any local observer (that is person 2) doesn't see any object passing by at a speed higher than the speed of light and light always is observed to move at the speed of light. He will, for instance, observe light rays moving outwards at the speed of light.

Dauto (talk) 02:45, 23 May 2010 (UTC)

May 23

Spider behaviour

In our shared house for university we have a dead spider that's been encased in some sort of plastic or wax near the ceiling for at least a year (before we moved in, damned if I'm gonna clean it!).

Today I've seen a big, similar sized spider climb up towards the dead spider about a day ago and it seems to be staying there up until this point of writing. It looks to be moving whilst up there too, and looks relatively healthy so I don't think it's dying.

That said, what would cause this sort of clinging behaviour to a dead, very-different-to-how-it-would-have-been-a-year-ago spider? Do spiders try to rescue their kind? Do they go off to die in similar places, or hang around with their dead counterparts? Is this just a coincidence and it might move in a couple of hours? Cheers!

Regards, --—Cyclonenim | Chat  02:32, 23 May 2010 (UTC)

You're presuming incorrectly that the source of the spider's attraction to that spot is the dead spider. Its attraction is to a good place to hang out; it would have no interest in the dead spider, but rather to that part of the ceiling itself. 63.17.50.130 (talk) 02:52, 23 May 2010 (UTC)

It certainly could move in a couple of hours, maybe to someplace you wouldn't like. If you want to dispose of it, try extending your vacuum cleaner's hose attachment, and the critter's last thought will be about how life sucks. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:57, 23 May 2010 (UTC)

Ha, yes maybe. Maybe it is a good place to hang out, but it's not even in a corner or somewhere remotely comfortable. It's just sitting on top of the dead spider. Regards, --—Cyclonenim | Chat  12:13, 23 May 2010 (UTC)

Would you rather live with a dead spider on your ceiling than to clean it? Dauto (talk) 03:31, 23 May 2010 (UTC)

Well it's never really been an issue, I guess it's hard to not sound disgusting unless you've actually seen where we're living. The place is an absolute shit hole as it is, a little dead, encased-in-wax spider from the previous occupiers isn't really going to bother me. Regards, --—Cyclonenim | Chat  12:13, 23 May 2010 (UTC)

How Spiders Work Count Iblis (talk) 16:42, 23 May 2010 (UTC)

Aircraft repairs, part 2

If the same saboteur as cut the generator wires also puts emery powder into the propeller pitch-change mechanism, could the damage be repaired by replacement/repair of parts and subsequent regreasing, or does it require replacing the whole screw? (Assume that the screw in question is a two-bladed Hamilton-Standard Hydromatic, if that helps.) 67.170.215.166 (talk) 03:07, 23 May 2010 (UTC)

• Hmmm, the wikipedia has a legal disclaimer, medical disclaimer, isn't it time for a "life critical systems disclaimer"? Right, I know that 67.170.215.166 wrote about a fictional setting, not real hardware, but what if one day someone takes wiki-advice on this matter seriously? East of Borschov (talk) 04:59, 23 May 2010 (UTC)

This kind of work is only done by licensed aircraft mechanics, and they know enough to always refer to the manual, not the Wiki reference desk. So there's no chance of this advice being taken seriously. 67.170.215.166 (talk) 05:57, 23 May 2010 (UTC)

Speaking of which, this being a reference desk, I suggest that you might consider referring to an aircraft mechanic. If you have trouble locating one, give me the identifier of your nearest local airport and I can see if I can help. Falconus^{p t c} 14:13, 23 May 2010 (UTC)

Stable ranges for Albedo and Emissivity of Earth

The Earth has a Global Annual Average Temperature of 14°C.
The Global Average Albedo is 0.30 and the concomitant Emissivity is 0.622.
Hence:
$T_{p}={\frac {((6.955\times 10^{8})^{2})\times (5778^{4})\times (1-0.3)}{(4\times 0.622\times 149597876600)^{2}}}={14}$
(derived from Luminosity)

So I was wondering how far that 14°C can shift and the planet still sustain some "liquid water,"
somewhere on the planet, what range is possible, and also what is range for the Albedo,
and the range for the Emissivity, for a stable habitable temperature for Earth life?
For clarity, this question is only about the Earth, as a reference point, not exo-moons.
Earth's temperature range is 60°C to -90°C, or 150 degrees.
There must be limits.
Global Annual Average Temperature Maximum: ??
Global Annual Average Temperature Minimum: ??
Minimum Albedo: ??
Minimum Emissivity: ??
Maximum Albedo: ??
Maximum Emissivity: ??
24.78.178.147 (talk) 01:30, 23 May 2010 (UTC)

I won't answer your question, but I will fix your equation.

$(T_{p}+273.15)^{4}={\frac {((6.955\times 10^{8})^{2})\times (5778^{4})\times (1-0.3)}{4\times 0.622\times (149597876600)^{2}}}=(13.78+273.15)^{4}$

T_p=13.78°C Dauto (talk) 05:48, 23 May 2010 (UTC)

Thanks, I missed that because I'm used to Excel not the code here.
((((((695500000)^2)*(5778^4)*(1-A)/(4*ε*(149597870690^2)))^0.25)-273.15) = 14.000
A=0.3
ε=0.62009
24.78.178.147 (talk) 04:42, 24 May 2010 (UTC)

Pineal gland

Is serotonin produced in the pineal gland? At present our article on this gland makes a big deal in the opening paragraph of serotonin as a product of the gland. If it's true, it's a secondary or minor function of the gland and the info needs to be moved further down. I'd rather cut it out, but need to be sure. Thank you. --Hordaland (talk) 07:14, 23 May 2010 (UTC)

I know melatonin is produced from serotonin in the pineal gland. (Melatonin in retina and in the digestive tract is a different story). Serotonin is produced from tryptophan, not sure where. --Dr Dima (talk) 08:25, 23 May 2010 (UTC)

What I mean by "not sure where" is as follows. The primary location of the serotonergic neurons in the human brain is the raphe nuclei (a part of the reticular formation) in the brainstem. What I'm not sure about is whether they produce most of their serotonin locally, or whether they "recycle" serotonin that is produced elsewhere. I'm pretty sure that serotonin is produced in the digestive tract, too. How much of it is produced in the pineal gland, how much in the raphe nuclei, and how much in the gut - I do not know. --Dr Dima (talk) 08:34, 23 May 2010 (UTC)

According to PMID 8745273, serotonin is indeed released by the pineal, although its main function there is to serve as precursor for melatonin. I believe the accepted concept is that serotonin serves as an autocrine hormone (i.e., affecting the pineal itself), rather than exerting significant effects elsewhere. Certainly the pineal, being a gland, does not send specific serotonergic projections to parts of the brain, as the Raphe nuclei do. Looie496 (talk) 16:50, 23 May 2010 (UTC)

Thank you for your answers, confirming what I suspected was the case! Meanwhile, someone else has fixed that paragraph, saving me the trouble. Hordaland (talk) 20:28, 23 May 2010 (UTC)

Intramuscular fat

I'm a bit lost here, so this could be a silly question, but I'm wondering if it's possible to sort of "target" certain types of body fat, in this case IMTG, when chosing a diet? Thinking retroactively, eating chips and french fries seems to have a larger effect on visceral fat, or at least a large effect, but is there any, healthier alternative that might have less of an effect on a certain, less desirable "unhealthy" fat types, and help to produce intramuscular fat (IMTG)? This is a bodybuilding/nutrition question! 210.254.117.185 (talk) 09:24, 23 May 2010 (UTC)

The relevant article is spot reduction, which says any kind of targeted fat loss is a myth - regrettably that article is pitifully underreferenced. -- Finlay McWalter • Talk 09:37, 23 May 2010 (UTC)

I wasn't asking about fat loss, I was asking about the increase of a certain type of fat. Even if it was related (though in reverse), IMTG and visceral fat are made by a difference process, where as the article you linked talks about the same type of fat on different parts of the body. 210.254.117.185 (talk) 10:16, 23 May 2010 (UTC)

CO2 and infrared radiation

If you double the concentration of CO₂ in a glass container, say from 0.03% to 0.06% (can't think why I chose those numbers!) what happens to the percentage of infrared radiation that will be absorbed? Does it double (i.e. it's a linear relationship) or does it only increase by say 25% (i.e. it's logarithmic). Hopefully someone has actually done an experiment to show this! 131.111.30.21 (talk) 11:07, 23 May 2010 (UTC)

The answer is given by the Beer–Lambert law - assuming that the absorbtion is linear with concentration - which I'm sure it will be. Also did you mean reflection of IR (as per global warming)?87.102.18.191 (talk) 11:22, 23 May 2010 (UTC)

So the absorption coefficient will double - this means the ratio of light passing through (before and after) will be:

e^-ax / e^-2ax = e² = 7.4 times less light after doubling the concentration.87.102.18.191 (talk) 11:32, 23 May 2010 (UTC)

Yea sorry, meant reflect. Does that change the figures above? 131.111.30.21 (talk) 12:11, 23 May 2010 (UTC)

I think so yes - will have to go and check.. (hang on)87.102.18.191 (talk) 12:33, 23 May 2010 (UTC)

Actually I think I was wrong to say that reflection of IR is the factor behind global warming.

The equations for reflected light will be those of scattering - however I'm not sure if the scattering is elastic or not - I think CO2 can reflect by Raman effect at least.

Someone else will need to answer this.87.102.18.191 (talk) 13:01, 23 May 2010 (UTC)

Clairfy: That would be 7.4 times less light NOT being absorbed (ie if 93% of light was absorbed before, then 7% escapes, after doubling CO2 only 1% escapes..)87.102.18.191 (talk) 13:44, 23 May 2010 (UTC)

In the case of the atmosphere the very low concentration is already enough to absorb most of the radiation so doubling makes little difference. However temperature is not relative to zero degrees Centigrade but absolute zero at -273°C so the 'little difference' can still mean a few degrees change. Dmcq (talk) 12:38, 23 May 2010 (UTC)

Where should I start?

1. Absorption of IR by CO₂ is the cause of greenhouse effect.
2. The equation used to get the figure 7.4 is completely wrong
3. The effect of the doubling of CO₂ concentration on how much IR gets absorbed depends on how thich is the path of the light through the container. If the path is thin enough that most of the radiation does get through, then doubling the concentration does double the absorption, but if the path is so thick that most of the radiation is already getting absorbed, then doubling the concentration has little effect. Think about it. If you look up at the sky through a canopy which has just a few liefs then doubling the number of liefs does double the fraction of the sky that's is covered but if you are looking through a canopy so thick that it already covers most of the sky than doubling the number of liefs has little effect.

Dauto (talk) 03:54, 24 May 2010 (UTC)

Can you explain 2 in more detail - assuming the atmosphere stays the same thickness - as an approximation, how is the Beer-Lambert law wrong here?87.102.85.123 (talk) 11:42, 24 May 2010 (UTC)

No, that is wrong. For the greenhouse effect, it is not relevant how much direct transmission there is ("how much sky can I see"), but how much light is transmitted at all, including diffuse light that has already interacted with one or more leafs. The canopy is actually not too bad an analogy. Even if you cannot see the sky at all, doubling the thickness of the canopy will reduce the amount of light that reaches the ground (for any given input). --Stephan Schulz (talk) 08:13, 24 May 2010 (UTC)

Ok that makes more sense, so it is logarithmic rather than linear? Does anyone do direct measurements of infrared reflection by the atmosphere? I.e. shine an infrared laser from somewhere like Mauna Loa Observatory to a satellite and then see how this is changing over time? 131.111.30.21 (talk) 08:49, 24 May 2010 (UTC)

Yes, overall climate sensitivity is logarithmic. In other words, doubling CO2 causes an equilibrium temperature increase of 3 degrees centigrade (roughly best current estimate, but there are fairly large error bands). Note that the earth has a lot of thermal inertia, so the effect lags the cause significantly. --Stephan Schulz (talk) 14:23, 24 May 2010 (UTC)

Sneezing during examinations

The last couple of years I've been noticing that I do a disproportionate amount of sneezing about 15 minutes into an examination, and I'm interested in why this might be. I don't suffer from hay fever, and I don't sneeze a lot generally. Could it be a reaction to the stress of exams? There's nothing to sneeze - my airway isn't blocked, for example - and once it's done I generally don't sneeze again. My other thought was a slight allergic reaction to the surroundings, but I've noticed it happening in two different examination halls. Of course, it could all be down to observation bias, or any number of other biases, but I don't think it is, and it does intrigue me, so I thought I might ask. Thanks, - Jarry1250 ^{[Humorous? Discuss.]} 13:04, 23 May 2010 (UTC)

• Was it an air-conditioned room? could be adjustment to AC or just some draft. Or, perhaps, simply adjustment to sitting (as opposed to active walking etc.). East of Borschov (talk) 13:21, 23 May 2010 (UTC)

Preparation of examination rooms often requires moving furntiture etc - maybe this produces a lot of dust?87.102.18.191 (talk) 13:45, 23 May 2010 (UTC)

Yes. Inhaling dust and sneezing are inextricably linked. I would also say, normally if a person finds themselves in a dusty room, they might open a window, or leave -- but when you're writing an exam, these are not good options ("Excuse me miss, you have to hand in your test before you leave. No you may not leave the room and then return. I can't allow that."). Unable to deal with the dust in this fashion, all they can do is keep breathing it in -- and sneezing to help keep the nasal passages clear and clean. Vranak (talk) 13:59, 23 May 2010 (UTC)

Dust seems like a good suggestion, the exam tables and whatnot must accumulate a load during the year. Previous locations may have been air-conditioned, but I'm 99% sure the place I'm sitting this years isn't (they open windows, doors, etc.) - Jarry1250 ^{[Humorous? Discuss.]} 14:29, 23 May 2010 (UTC)

At my old school they placed down canvas tarpaulins on the gymnasium floor for examinations. I'm fairly sure they got no use apart from the exams in January and June, so I suspect a lot of dust would be stirred up whenever they got moved or walked on. Always had to take an anti-histamine tablet on the day of an exam, since sniffles were a problem. Brammers (talk) 10:57, 24 May 2010 (UTC)

Why does sugar make things less sour?

So lets say you are making lemonade. Why is it that sugar makes it less sour? Does the sugar flavor overpower the sour flavor, or does it negate it? Or I should ask, would other flavors, like salt (saltiness) for example, make it less sour as well? ScienceApe (talk) 15:56, 23 May 2010 (UTC)

Sourness is due to acidity Taste#Sourness - adding sugar doesn't affect the acidity. Lemonade sourness is in part due to the citric acid , and also due to dissolved carbon dioxide (if it's fizzy type). There's not a reaction between sugar and citric acid to be expected in lemonade (though it could possible esterify) I'm fairly certain it is a masking effect.87.102.18.191 (talk) 16:25, 23 May 2010 (UTC)

Sweetness competes with each of the other basic tastes (sour, salty, bitter), in the sense that increasing sweetness reduces the perception of the others, and increasing the others reduces the perception of sweetness. A notable example is tonic water, which doesn't seem sweet to many people even though it is almost gooey with sugar. I'm not sure whether the other basic tastes compete with each other (sour versus bitter or sour versus salty, for example). Looie496 (talk) 16:39, 23 May 2010 (UTC)

There's a significant difference between the taste of "straight" tea and coffee, which tend to be bitter, vs. adding sugar to them. The one I'm not sure you can do much about is saltiness. I can't think of any obvious way to counter saltiness other than simply diluting it (as you could with the other items as well). ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:30, 23 May 2010 (UTC)

The old wives' way of adding a potato to oversalted stews (and then discarding the potato, which will have absorbed the excess salt) does work. Never tried it for anything else, though. --TammyMoet (talk) 09:59, 24 May 2010 (UTC)

Has anyone seen Neptune with the naked eye?

Although it is commonly claimed that Neptune is too faint to be seen with the naked eye, this is not really true.

Brian skiff has tried but he failed to see it. The conditions were not optimal as Neptune was low in the sky. He claims that from the Southern Hemisphere it would be straightforward to spot. So, this suggests that there should be quite a few (amateur) astronomers with excellent eyesight who have seen it, but I haven't seen any such claims. Count Iblis (talk) 17:53, 23 May 2010 (UTC)

At a magnitude of ~8-7.78, it would require exceptional conditions to see it: an experienced astronomer who knows how to look for faint objects, exceptionally clear sky, hundreds of kilometers from any city, and knowing exactly where to look. Even if you could, by some miracle, manage to see it, I'm not sure that you could distinguish it from any other faint star out there. Do you know the positions of the tens of thousands of stars at least that bright with a high enough degree of precision to distinguish one barely visible point of light from another one? As the forum points out, even Uranus, with a magnitude of up to 5.32, and 4 Vesta, of magnitude up to 5.1, were not discovered and named until telescopes were around. I would hazard a guess that most celestial objects dimmer than magnitude 5 were not cataloged and named until after the invention of the telescope. Now granted, "named and recognized" is not the same thing as "ever seen", but if you can't recognize a faint dot as Neptune, do we really count that as "seeing" it? Buddy431 (talk) 18:22, 23 May 2010 (UTC)

Yes, "seeing Neptune" with the naked eye would be a tour de force involving detailed star charts and identifying all the brighter objects in the immediate neighborhood. But note that quite a few (amateur) astronomers do exactly this sort of a thing as a sport, but usually for spotting Messier objects with the naked eye. They keep logs of successful naked-eye observations, see e.g. here. So, given this dedicated effort, I find a bit strange that only [Brian Skiff's report] of his failure to see Neptune exists. Count Iblis (talk) 00:24, 24 May 2010 (UTC)

Incidentaly, Wikipedia doesn't have a comprehensive list of astronomical objects (or even stars) by magnitude that's very good. We have the List of brightest stars going down to magnitude 2.5. It would be nice if we could get lists for the other ranges (i.e. List of stars with magnitude 2.5-3.5, list of stars with magnitude 3.5-4.5, etc). If there are machine readable star catalogs available, such lists could be made with some sort of bot. Of course, such lists may be seen as "indiscriminate" by the deletionists here... Buddy431 (talk) 18:49, 23 May 2010 (UTC)

The problem with such a table is that the number of stars at magnitude X grows exponentially in X (there are roughly 3 times more stars with magnitude 2.5-3.5 than with magnitude 1.5-2.5, and another 3 times more with 3.5-4.5). So you get into really large numbers really fast - and I suspect for most of these stars we have very little information. --Stephan Schulz (talk) 11:41, 24 May 2010 (UTC)

No fish

Is there a term for someone who eats meat, fruit and vegetables but doesn't eat any fish? Servien 18:47, 23 May 2010 (UTC)

Closest I've found so far is Pollotarianism, which excludes fish and mammals. Vimescarrot (talk) 18:53, 23 May 2010 (UTC)

Are there enough people that fit that description to warrant having a name for it? --Tango (talk) 19:17, 23 May 2010 (UTC)

I know two. They can eat mammals such as whale but are highly allergic to all fish (salt water and fresh), seafood and crustaceans. It is one of the nine most common food allergies. Kittybrewster ☎ 19:29, 23 May 2010 (UTC)

Reverse pescetarian? Clarityfiend (talk) 20:23, 23 May 2010 (UTC)

How does anti-pescatarian sound? Or just apescatarian. Vranak (talk) 21:03, 23 May 2010 (UTC)

Like they wouldn't eat fruits or vegetables either. Clarityfiend (talk) 21:09, 23 May 2010 (UTC)

Pesca- just means fish though. Apesca = no fish. Vranak (talk) 21:33, 23 May 2010 (UTC)

Heh, nice term. I guess that applies to me. I eat meat, vegetables and fruit, but I'm not a fan of fish so I don't eat it. Regards, --—Cyclonenim | Chat  22:33, 23 May 2010 (UTC)

Of course it's hard not to notice that the first part of the term forms the words ape scat. Vranak (talk) 22:47, 23 May 2010 (UTC)

Jane Brody has used the term "pescaphobia". Looie496 (talk) 22:58, 23 May 2010 (UTC)

That implies an irrational fear of fish, but if one is allergic, it's a rational fear, and if one simply doesn't like the taste of fish, that's neither irrational nor a fear, it's just personal preference. That does not preclude the possibility that there could be some having an irrational fear of fish. However, terms like vegetarian and vegan are preferred over "carniphobia" or whatever the equivalent would be. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:03, 23 May 2010 (UTC)

Bird call

What bird is this? http://commons.wikimedia.org/wiki/File:Unknown_bird_call_MN_052210.ogg

Taken 2010-05-22 in Interstate State Park. I was not able to see the bird making this call (all weekend!).

-Ravedave (talk) 20:37, 23 May 2010 (UTC)

Dragons

Are we absolutely sure that dragons have never existed? I find it interesting that almost every part of the world has stories about dragons of some form or another. Seems strange for something that was never real. If there *were* dragons (not saying fire breating and flying, which AFAIK would be impossible - just really big carnivorous reptiles, or even the long, thin, Chinese-style water-based ones) and their numbers were declining at around the same time that humans were becoming civilized, and the last few had been wiped out before 1000AD (say), would there even be any ovbious evidence today of their existence? Just curious. --95.148.108.186 (talk) 21:06, 23 May 2010 (UTC)

If they don't breathe fire or fly, why would anybody call them dragons instead of "just really big carnivorous reptiles"? Clarityfiend (talk) 21:14, 23 May 2010 (UTC)

Because they were stories of heroism that were exaggerated in the telling and re-telling? Going from a dinosaur/big lizard-like creature, to something with borderline magical powers? Don't know really, I was just thinking on the screen. :) --95.148.105.95 (talk) 21:25, 23 May 2010 (UTC)

Really big carnivorous reptiles? Like crocodiles and alligators? Or dinosaurs? They definitely exist(ed). --Tango (talk) 21:20, 23 May 2010 (UTC)

Or Pterosaurs? ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:45, 23 May 2010 (UTC)

Or Komodo dragons? "really big carnivorous reptiles" ... check, check, and check. We even call them "dragons". -- 174.24.200.38 (talk) 01:24, 24 May 2010 (UTC)

I believe the biggest issue is that dragons have, by classical definition, six appendages (four legs and two wings), while (and correct me if I'm wrong), all other higher land-going lifeforms have four. Snakes of course don't count; they have none. But six, no, that just doesn't seem feasible from an evolutionary standpoint. And then there's the small matter of there being no fossil record of such a thing. Vranak (talk) 21:31, 23 May 2010 (UTC)

Take a look at draco (genus). Looie496 (talk) 22:54, 23 May 2010 (UTC)

Fair enough! I'll revise that 'classical definition' then -- four legs and flappable wings, for more than just gliding. Vranak (talk) 23:19, 23 May 2010 (UTC)

two points, both from Dragon

• in Origin and Etymology "Dinosaur and mammalian fossils were occasionally mistaken for the bones of dragons and other mythological creature; for example, a discovery in 300 BC in Wucheng, Sichuan, China, was labeled as such by Chang Qu...." ... more in that section
• in Dragon#Indian , after removing hyperbole, appears to be a description of a Python

Anyway , if it didn't exist you'd have to invent it .. those long cavemen evenings without TV, and kids always asking "what is there over there/below"87.102.18.191 (talk) 21:37, 23 May 2010 (UTC)

I'm also likely to believe the idea of dragons being an exaggerated folk memory (of v. big snakes and crocs) - reason - apparent absense of dragon myths in countries that do have big snakes and crocs.87.102.18.191 (talk) 21:43, 23 May 2010 (UTC)

Folk memory, yes. Perhaps as with other mythical creatures, e.g. the unicorn. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:47, 23 May 2010 (UTC)

They probably come from descriptions of rhinoceri. (original research?) --Kurt Shaped Box (talk) 21:54, 23 May 2010 (UTC)

I've heard that theory before. And there typically weren't any rhinos in Europe, just the Rhineland, which is unrelated as far as I know. There's a much more modern analogy, though, and that is the current stereotype of what flying saucer aliens look like, i.e. like the characters in Close Encounters and E.T., which apparently evolved over time from the appearance of primitive crash-test dummies used in high-stratosphere balloon tests. This contrasts with The Day the Earth Stood Still, where the aliens looked like Michael Rennie. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:00, 23 May 2010 (UTC)

Which, trust me, was a lot more scary. HalfShadow 22:01, 23 May 2010 (UTC)

Yep. Klaatu barada nikto, and all that sort of thing. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:03, 23 May 2010 (UTC)

I have to ask -- I know this phrase from Army of Darkness, but does it have any deeper/earlier meaning? Vranak (talk) 23:18, 23 May 2010 (UTC)

We have an article on it, which I've now linked. Without looking at it first, I know "Klaatu" was the name of the alien played by Michael Rennie, and the whole phrase was spoken to the robot Gort, which somehow told him where to find Klaatu. That's a lot of info to be contained in 2 words, but the robots were programmed with a series of commands which were like shorthand of some kind. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:26, 23 May 2010 (UTC)

Also note that different parts of the world having stories about "dragons" is not terribly telling. A Chinese dragon isn't all that similar to a European dragon other than the fact that they're both mythical reptiles. Do big, scary (or auspicious, depending on your point of view) exist? Absolutely. Buddy431 (talk) 23:01, 23 May 2010 (UTC)

I have heard it proposed, though not directly by the experts of the field, that it goes way back. When our mammalian ancestors were evolving, there were still dinosaurs around. It would stand to reason that early mammals would have been extraordinarily cautious about large carnivorous reptilian animals. The theory that was proposed is that the reason that many human cultures have a dragon of sorts is just because those descriptions stand out to us on residual instinct. Now is that likely after 65 million years? I have no clue, maybe someone else can comment. Falconus^{p t c} 00:27, 24 May 2010 (UTC)

Hey, this seems to be directly related to what I just said above. An Instinct for Dragons.Falconus^{p t c} 00:33, 24 May 2010 (UTC)

I try to refrain from just giving comments which don't add to the discussion, but i have to say the above is just absolutely fascinating! What an amazing hypothesis. Vespine (talk) 00:55, 24 May 2010 (UTC)

I also heard that theory long ago. I think it was termed "racial memory". It seems a little far-fetched. However, humans often show a fear and distrust of reptiles in general, including the serpent in Genesis as just one example. Whether that's "racial memory" going back to times when mammals and dinosaurs may have co-existed, or if it's just good sense, is hard to say. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:36, 24 May 2010 (UTC)

On the subject of "pre-programmed" fear or knowledge of serpents - the plant/drug Yage is commonly reported to produce hallicinations of predators such as big cats/snakes.. even in people brought up in countries with no such thing [21] (also [22]) (it was reported possibly less reliably by Terence McKenna that even eskimos hallucinate cat predators under it's influence) If that is someway related to some sort of built in DNA memory of giant reptiles is tenuous .. It's not as far as I know been shown that people with no concept of cats / snakes hallucinate them under it's influence. Probably irrelevant.87.102.18.191 (talk) 01:33, 24 May 2010 (UTC)

Right. It is highly doubtful the "genetic memory of the dinosaurs as the arch-nemesis of humans" hypothesis has any merit at all. At the time dinosaurs went extinct our ancestors were not even monkeys; actually, at the time of the last dinosaurs the lemurs and the tarsiers did not yet split into separate lines (we are on the "tarsier" line, haplorrhini, in case you wonder). Big cats, hippos, and early hominids / humans were and are until this day a much more real and a much more present threat to our ancestors. Yet we do not have much of a natural fear of cats, large herbivores, or other people. What humans usually fear are bacteria, viruses, cockroaches, snakes, and spiders. People go to the zoo to see the tiger; people run away when they see a garter snake. A flying snake should be an outright nightmare. Hence, I guess, is the dragon. --Dr Dima (talk) 01:36, 24 May 2010 (UTC)

There are plenty of tropes which tend to occur independently in all sorts of cultures and stories. Like superhuman strength - how many people do you think in the history of man have been carrying something and thought it would be really neat if they could pick up the whole load in one hand? Or flight - all kinds of legends and myths talk about people soaring through the sky, not because humans ever had the ability to fly, but because it's almost universally held that it would be awesome. ZigSaw 11:51, 24 May 2010 (UTC)

over eating

If a person is disabled or older they cannot do as much exercise as may be needed for weight control. Therefore weight control is dependent on not over eating. Yet because the human body requires so little food it is very easy to over eat. Is there a pill or other means of controlling appetite so that a person will not over eat due to a feeling of hunger? 71.100.3.228 (talk) 21:24, 23 May 2010 (UTC)

There are lots of appetite suppressants available. I won't comment on their efficacy or safety, but they certainly exist. --Tango (talk) 21:45, 23 May 2010 (UTC)

What about other means besides pharmaceuticals? Are their foods or other means to control or eliminate appetite? 71.100.3.228 (talk)

I've heard of the opposite effect, i.e. that places like McDonalds used to put chemicals into your food which made you feel full slower, and thus more likely to buy more food. Regards, --—Cyclonenim | Chat  22:31, 23 May 2010 (UTC)

Regards what? 71.100.3.228 (talk) 04:27, 24 May 2010 (UTC)

"Regards" is a formal way of ending a letter. I don't see it much in Web postings, but that's what Cyclonenim meant. Comet Tuttle (talk) 06:58, 24 May 2010 (UTC)

It works better for starting threads than replying to them, but it's part of the signature and I sure as hell can't be arsed to write it out every time (i.e. think when it's needed). Regards, --—Cyclonenim | Chat  07:32, 24 May 2010 (UTC)

When I see it at the end of a web post I'll continue then to append (the word) nothing. 71.100.3.228 (talk) 08:47, 24 May 2010 (UTC)

Studies have shown that the feeling of satiety comes from bulk, not calories. Eat lots of vegetables and fresh fruits - bulk without much calories - and wheat- or oat-fibre too to fill you up. Avoid foods containing fat, especially saturated fat (although a small amount of fat is required for health). See http://www.nutritiondata.com/topics/fullness-factor After a few months you will prefer healthy food and be disgusted by fatty junk food. 92.28.255.202 (talk) 22:24, 23 May 2010 (UTC)

Byetta is a powerful appetite suppressant, which also delays emptying of the stomach. It is presently commonly used as a prescription drug for Type 2 diabetics, but might be the next big weight loss drug. The article notes some undesirable side effects of the drug. Edison (talk) 00:44, 24 May 2010 (UTC)

For severe cases of obesity, where the standard advice of diet and exercise does not work, bariatric surgery has been used to reduce the size of the stomach. A smaller stomach means that less food is needed to obtain satiety. -- 174.24.200.38 (talk) 01:20, 24 May 2010 (UTC)

The diet market is massive, so you'll hear hundreds of claims of "miracle diets" and "pills". Even moderate exercise can help though. Under normal conditions weight gain or loss is down to the amount of energy you use, minus the energy you take in from food (calories). You can increase your use of energy as well as decrease your intake and it works very well. FT2 ^{(Talk | email)} 04:17, 24 May 2010 (UTC)

This remedy is where the problem begins... exercise only increases hunger making the task to reduce intake even harder. 71.100.3.228 (talk) 04:25, 24 May 2010 (UTC)

No, I read about a study which said that although people did eat more after exercise, the extra calorie intake was still less than that expended. So there is no excuse for not exercising. Never mind the drugs - a simple thing to do, without possible bad side-effects, is to make sure you eat enough fresh vegetables and fruit each day. Something in my experience that may block this is that many people in my experience do not know how to do simple cooking, such as boiling vegetables (cut into chunks and put in a saucepan of boiling water for a few minutes until tender), and so have to buy junk food instead. 92.28.251.49 (talk) 11:13, 24 May 2010 (UTC)

help pLz \\ drugs used in managment of infusion

describe the drugs used in managment of infusion - related to side effects —Preceding unsigned comment added by Mrmr-rana (talk • contribs) 21:33, 23 May 2010 (UTC)

You're going to need to be much more specific if you want a meaningful answer. What type of infusion do you mean? Also note that we cannot give medical advice on the reference desk. If this is about a treatment you or someone you know is undergoing, you should talk to the doctor who's administering the treatment. Buddy431 (talk) 22:56, 23 May 2010 (UTC)

Possibly means "Blood infusion" ie Blood transfusion - an anticoagulant is Heparin, Paracetamol is used if minor side effects occur [23] not a medician so don't know much more.87.102.18.191 (talk) 00:32, 24 May 2010 (UTC)

This looks more like a homework question than a request for medical advice to me. AndrewWTaylor (talk) 08:18, 24 May 2010 (UTC)

I really hope it is, I'd hate for the triage nurses to have brought in a wireless laptop just to have the physician's Reference Desk question get rejected ZigSaw 11:39, 24 May 2010 (UTC)

Tiny bullet-shaped dog

I saw the tiniest dog I've ever seen being taken for a walk recently. It was white and bullet shaped, with the head forming the curved cone-like front of the bullet. Moving at walking pace, its little short legs were a blur, as its stride could only have been one or two inches. It was not a sausage-dog or a chichua. It did not behave like a puppy, but like a disciplined fully-grown dog. What breed could it have been? 92.28.255.202 (talk) 22:21, 23 May 2010 (UTC)

Sounds more like a pet guinea pig to me. 71.100.3.228 (talk) 22:38, 23 May 2010 (UTC)

or White rat on a lead ? (it happens).87.102.18.191 (talk) 22:44, 23 May 2010 (UTC)

What was its coat like? And it's not a Scottish Terrier is it? Vranak (talk) 22:46, 23 May 2010 (UTC)

It was not a guinea pig or a Scottish terrier. It had short fur. 92.28.255.202 (talk) 22:49, 23 May 2010 (UTC)

Sure it wasn't a ferret? --Kurt Shaped Box (talk) 22:51, 23 May 2010 (UTC)

It was definately a dog, and not a rat or ferret. 92.28.255.202 (talk) 22:53, 23 May 2010 (UTC)

Try teacup dog. 71.100.3.228 (talk) 23:06, 23 May 2010 (UTC)

It may have been something like a Bull Terrier (Miniature) except it had no neck, and shorter legs. Apparantly there are "designer dogs", so perhaps it had been specially bred to be super-tiny. 92.28.255.202 (talk) 23:14, 23 May 2010 (UTC)

Maybe a Pomeranian (dog)? —Preceding unsigned comment added by 86.4.186.107 (talk) 07:52, 24 May 2010 (UTC)

In case you haven't found it yet, the article on List of dog breeds gives you loads of pictures. If you were in Yorkshire, it's likely to have been a ferret.--Shantavira|^{feed me} 08:48, 24 May 2010 (UTC)

It was not a pomeranian as it did not have a fluffy coat, and a pomeranian is not bullet shaped either. Perhaps I underestimated the stride - it may have been more like three inches. I have seen ferrets being taken for a walk on one or two other another occassions, and it was definately not a ferret. If miniature Bull Terrier puppies have short legs and no neck, then it could have been one of them. As it had to concentrate on moving its little short legs as fast as propellors, then it may not have had time to indulge in the usual romping puppy behaviour. My best guess is that it was a cross between a minature Bull Terrier and some other minature dog that gave it tiny legs and no neck. 92.28.251.49 (talk) 11:00, 24 May 2010 (UTC)

May 24

OIL SPILLS

Technically aren't asphalt highways just oil spills mixed with dirt? 71.100.3.228 (talk) 02:26, 24 May 2010 (UTC)

No. Part of the definition of "spill" is that it is accidental. Also, asphalt is a specific component of crude oil, rather than crude oil itself. --Tango (talk) 02:32, 24 May 2010 (UTC)

That's right — fractional distillation is used to separate crude oil into things like gasoline, kerosene, and asphalt. But then the asphalt is indeed mixed with dirt; our asphalt article, in its Rolled asphalt concrete section, states that an asphalt highway is actually only 5% asphalt itself, and 95% "aggregates", meaning gravel, sand, and stones. Comet Tuttle (talk) 06:56, 24 May 2010 (UTC)

acetone

does acetone evaporate like alcohol or does it leave a residue? can u use it on food surfaces? —Preceding unsigned comment added by Tom12350 (talk • contribs) 03:37, 24 May 2010 (UTC)

Yes, it evaporates very quickly, maybe not as quickly as most alcohols though. No, I would never use it on anything that would ever contact food. Beach drifter (talk) 03:44, 24 May 2010 (UTC)

After a little reading, it appears to be hardly toxic at all. I still see no reason you would need to use it in the kitchen. Beach drifter (talk) 03:47, 24 May 2010 (UTC)

can i use it on a plastic counter top, and a particle board kitchen table with a wood looking plastic/ vinyl vanear —Preceding unsigned comment added by Tom12350 (talk • contribs) 04:11, 24 May 2010 (UTC)

It's a solvent, so plastic-based and printed food surfaces might get damaged, or colors from packaging transfer. What would you intend to use it for? FT2 ^{(Talk | email)} 04:12, 24 May 2010 (UTC)

There are lots of products specifically designed for this use, visit your local supermarket. Vespine (talk) 04:50, 24 May 2010 (UTC)

No. Don't use it on those - it will dissolve them, then evaporate, leaving an impossible to clean mess. Not really a mess - more like a mushy smear of the veneer. It's pretty non-toxic though (it's actually legal as a food additive!), and does not leave any residue behind, so in that regard it's safe in the kitchen. I use acetone to remove stickers. But you have to work VERY fast, it evaporates very quickly - even the open bottle will evaporate. Put the acetone on a tissue, and rub the sticker - don't put the acetone on the sticker, it will dissolve the glue, then run, leaving a bigger sticky spot than when you started. Ideally have a second person to cap the bottle in between putting some on the tissue. Acetone is probably the fastest evaporating solvent commonly available. Ariel. (talk) 05:32, 24 May 2010 (UTC)

A little WD-40 will remove stickers as well and there's no bottle to close. Dismas|^(talk) 08:10, 24 May 2010 (UTC)

how will plastic-based and printed food surfaces get damage if they use it in labs to clean plastic labware? will it help if i dilute it 50-50 w/water? —Preceding unsigned comment added by Tom12350 (talk • contribs) 06:13, 24 May 2010 (UTC)

Not every plastic is the same, some will be totally unaffected, others will dissolve into goo - there are a LOT of different kinds of plastic. I don't know what water will do, probably it will slow down the dissolving. Ariel. (talk) 08:08, 24 May 2010 (UTC)

arent there only 7 kinds of plastic? —Preceding unsigned comment added by Tom12350 (talk • contribs) 08:41, 24 May 2010 (UTC)

Category:Plastics. 212.219.39.146 (talk) 08:47, 24 May 2010 (UTC)

There are many more! I used acetone in the lab and I saw somebody cleaning a keyboard. The Grey keys like Strg And Alt got very soft and the printed letters vanished, the other white keys showed no problem and ended up very clean.--Stone (talk) 09:37, 24 May 2010 (UTC)

The better cleaning agent for you might be, what other people use for disinfection, it is a mixture of 70% isopropanol and water.--Stone (talk) 09:37, 24 May 2010 (UTC)

i already tried that. will it help if i dilute acetone 50-50 w/water? —Preceding unsigned comment added by Tom12350 (talk • contribs) 10:49, 24 May 2010 (UTC)

That would slow its evaporation, but it would also slow its cleaning abilities, so there would be no net difference. You can put it in a spray bottle, not a mist one, a squirt one. --Chemicalinterest (talk) 11:02, 24 May 2010 (UTC)

i dont understand. if i dilute it wont it be less corrosive? —Preceding unsigned comment added by Tom12350 (talk • contribs) 11:14, 24 May 2010 (UTC)

Yes diluting it will make it less likely to damage the plastic. Alchohol is a better choice though if you have it. What are you cleaning?87.102.85.123 (talk) 11:47, 24 May 2010 (UTC)

I used to be a follower of the "throwing assorted chemical compounds on a surface makes it cleaner" school of thought, I must admit, but a lot of 'em will ruin your crap if you aren't careful. The way I see it, just because something kills bacteria and viruses doesn't mean it's safe for you to eat. It's not that antiseptics and antibac soap are actually making the surface cleaner on a microscopic scale - they're simply poisons designed to kill microbes instead of humans. Which is why you're supposed to wipe away the disinfectant before you eat off something you use it on. In the same vein, just because something is caustic doesn't mean it's necessarily going to clean whatever you put it on. And if its effects are 75% "creating a goopy catastrophe" and 25% "cleaning the surface", no matter how much you dilute it you're still going to get three times as much goop as cleaning action. ZigSaw 11:46, 24 May 2010 (UTC)

Crystal Violet

Hi there :) My name is Elin and I'm from Sweden. Right now I'm writing an assay about terraforming in astrobiology with chemistry and biology as "main subjects". I'm now stuck on gram staining and I really need to know how crystal violet is produced. When I read this article: http://en.wikipedia.org/wiki/Crystal_violet, I don't quite get the production. Mostly it's because I don't understand everything that is written, for example I don't get if it's ment that it is redox (gain) or oxidation (loss) that happens when you oxidize the compund in the second prodction step. And what about the last step? Is that the final step to get crystal violet, or is it a step to produce something else since it says "Hydrolysis of crystal violet gives the carbinol"? And what is a leuco? I've written about the first two steps, but I've left out what I've asked about (the oxidize-question, leuco and the third step). I feel like I should bring more to the table in order to get a higher grade and it would be sad if difficulties with language should stop me from getting the grade that I need. Please try and explain clearly and detailed. I don't mean that I want it to be simple, just that i'm thankful if you explain a lot since I don't understand all english words. Thanks a lot! /Elin —Preceding unsigned comment added by Ailithey (talk • contribs) 08:56, 24 May 2010 (UTC)

The leuco (white or colourless) form is oxidized with oxygen. The carbinol is a alcohol derived from methanol by substituting the hydrogen by something different, here the central C-OH is attached to three 4-dimethylaminopheny substituents.--Stone (talk) 09:46, 24 May 2010 (UTC)

The German article Kristallviolett has a better image what happens.--Stone (talk) 09:49, 24 May 2010 (UTC)

Gentian violet and Crystal_violet are the same substance, but the Gentian violet is about the medical use!--Stone (talk) 09:53, 24 May 2010 (UTC)

Thanks a lot, I'm starting to get it. But if you look at the article http://en.wikipedia.org/wiki/Crystal_violet, I still don't really get the production. The ast step says this: A typical oxidizing agent is manganese dioxide. Hydrolysis of crystal violet gives the carbinol: [C(C6H4N(CH3)2)3]Cl + H2O → HOC(C6H4N(CH3)2)3 + HCl Is this step part of the production of crystal violet? Do you get crystal violet by following all three steps, or is the last step the formula for the production of a carbinol? —Preceding unsigned comment added by Ailithey (talk • contribs) 10:38, 24 May 2010 (UTC)

The article was a bit confusing - I've changed it to avoid confusion - http://en.wikipedia.org/w/index.php?title=Crystal_violet&oldid=363908374

It should be clear now. The last step was not part of production. 87.102.85.123 (talk) 12:06, 24 May 2010 (UTC)

center of mass

why does objects rotate around it's centre of mass ..? I mean as a example, when we throw a rod (something like that) in the air holding at the edge,we can see it rotates around its CM.dany (talk) 13:19, 24 May 2010 (UTC)

Try to imagine an object that does not rotate around its CoM. Then that would mean that the CoM of the object would rotate around some point (inside or outside of the body). Therefore the CoM would be accelerating toward the point of rotation (centripetal acceleration). That would require an external force. Count Iblis (talk) 14:06, 24 May 2010 (UTC)